Primoris Services (PRIM) 10-Q5 Nov 132013 Q3 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2013	Nov. 06, 2013
Document and Entity Information	'	'
Entity Registrant Name	'Primoris Services Corp	'
Entity Central Index Key	'0001361538	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-13	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--12-31	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	51,571,394
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:	'	'
Cash and cash equivalents	$174,034	$157,551
Short term investments	3,179	3,441
Customer retention deposits and restricted cash	15,377	35,377
Accounts receivable, net	284,497	268,095
Costs and estimated earnings in excess of billings	80,434	41,701
Inventory and uninstalled contract materials	43,616	37,193
Deferred tax assets	10,477	10,477
Prepaid expenses and other current assets	12,830	10,800
Total current assets	624,444	564,635
Property and equipment, net	220,179	184,840
Investment in non-consolidated entities	6,546	12,813
Intangible assets, net	48,002	51,978
Goodwill	118,626	116,941
Other long-term assets	1,214	'
Total assets	1,019,011	931,207
Current liabilities:	'	'
Accounts payable	119,882	151,546
Billings in excess of costs and estimated earnings	147,464	158,892
Accrued expenses and other current liabilities	101,881	76,152
Dividends payable	1,805	'
Current portion of capital leases	3,928	3,733
Current portion of long-term debt	26,910	19,446
Current portion of contingent earnout liabilities	8,763	10,900
Total current liabilities	410,633	420,669
Long-term capital leases, net of current portion	2,760	3,831
Long-term debt, net of current portion	188,713	128,367
Deferred tax liabilities	20,018	20,018
Long-term contingent earnout liabilities, net of current portion	6,083	12,531
Other long-term liabilities	13,243	13,153
Total liabilities	641,450	598,569
Commitments and contingencies	'	'
Stockholders' equity	'	'
Common stock-$.0001 par value, 90,000,000 shares authorized, 51,571,394 and 51,403,686 issued and outstanding at September 30, 2013 and December 31, 2012	5	5
Additional paid-in capital	159,058	155,605
Retained earnings	217,540	175,517
Noncontrolling interests	958	1,511
Total stockholders' equity	377,561	332,638
Total liabilities and stockholders' equity	$1,019,011	$931,207

CONDENSED_CONSOLIDATED_BALANCE1

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
CONDENSED CONSOLIDATED BALANCE SHEETS	'	'
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	51,571,394	51,403,686
Common stock, shares outstanding	51,571,394	51,403,686

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
CONDENSED CONSOLIDATED STATEMENTS OF INCOME	'	'	'	'
Revenues	$551,333	$431,842	$1,406,341	$1,060,851
Cost of revenues	475,868	375,551	1,225,243	922,960
Gross profit	75,465	56,291	181,098	137,891
Selling, general and administrative expenses	36,478	26,014	96,657	69,684
Operating income	38,987	30,277	84,441	68,207
Other income (expense):	'	'	'	'
Income (loss) from non-consolidated entities	113	-159	169	895
Foreign exchange gain (loss)	91	18	3	-30
Other expense	-376	-382	-809	-961
Interest income	32	96	95	143
Interest expense	-1,579	-937	-4,501	-3,044
Income before provision for income taxes	37,268	28,913	79,398	65,210
Provision for income taxes	-14,075	-10,965	-30,272	-24,875
Net income	23,193	17,948	49,126	40,335
Less net income attributable to noncontrolling interests	-1,348	-432	-1,947	-600
Net income attributable to Primoris	$21,845	$17,516	$47,179	$39,735
Earnings per share:	'	'	'	'
Basic (in dollars per share)	$0.42	$0.34	$0.92	$0.77
Diluted (in dollars per share)	$0.42	$0.34	$0.91	$0.77
Weighted average common shares outstanding:	'	'	'	'
Basic (in shares)	51,568	51,398	51,529	51,387
Diluted (in shares)	51,671	51,404	51,595	51,402

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:	'	'
Net income	$49,126	$40,335
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation	31,003	20,719
Amortization of intangible assets	5,576	4,669
Gain on sale of property and equipment	-1,176	-2,396
Income from non-consolidated entities	-169	-895
Impairment expense for non-consolidated entities	3,250	'
Non-consolidated entity distributions	3,186	1,260
Stock-based compensation expense	229	'
Changes in assets and liabilities:	'	'
Customer retention deposits and restricted cash	20,000	-3,324
Accounts receivable	-16,402	-64,933
Costs and estimated earnings in excess of billings	-38,733	-21,089
Other current assets	-8,665	475
Accounts payable	-32,551	20,433
Billings in excess of costs and estimated earnings	-11,428	7,329
Contingent earnout liabilities	-9,287	-2,489
Accrued expenses and other current liabilities	26,626	20,688
Other long-term liabilities	90	-1,510
Net cash provided by operating activities	20,675	19,272
Cash flows from investing activities:	'	'
Purchase of property and equipment	-68,749	-23,720
Proceeds from sale of property and equipment	6,554	7,683
Purchase of short-term investments	-5,620	-6,380
Sale of short-term investments	5,882	23,000
Cash paid for acquisitions	-2,273	-38,110
Net cash used in investing activities	-64,206	-37,527
Cash flows from financing activities:	'	'
Proceeds from issuance of long-term debt	97,035	16,671
Repayment of capital leases	-3,399	-8,018
Repayment of long-term debt	-29,225	-12,177
Repayment of subordinated debt	'	-17,501
Proceeds from issuance of common stock purchased by management under long-term incentive plan	1,455	1,240
Dividends paid	-3,352	-4,611
Payment of accumulated earnings to non-controlling interest holder	-2,500	'
Repurchase of common stock	'	-1,001
Net cash provided by (used in) financing activities	60,014	-25,397
Net change in cash and cash equivalents	16,483	-43,652
Cash and cash equivalents at beginning of the period	157,551	120,306
Cash and cash equivalents at end of the period	174,034	76,654
Cash paid during the period for:	'	'
Interest	3,369	2,282
Income taxes, net of refunds received	32,379	18,082
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES	'	'
Obligations incurred for the acquisition of property and equipment	2,523	1,854
Dividends declared and not yet paid	$1,805	$1,542

Nature_of_Business

Nature of Business	9 Months Ended
Nature of Business	Sep. 30, 2013
Nature of Business	'
Nature of Business	'
	Note 1—Nature of Business

	Organization and operations— Primoris Services Corporation is a holding company of various construction and product engineering subsidiaries. The Company’s underground and directional drilling operations install, replace and repair natural gas, petroleum, telecommunications and water pipeline systems, including large diameter pipeline systems. The Company’s industrial, civil and engineering operations build and provide maintenance services to industrial facilities including power plants, petrochemical facilities, and other processing plants; construct multi-level parking structures; and engage in the construction of highways, bridges and other environmental construction activities. The Company is incorporated in the State of Delaware and its corporate headquarters are located at 2100 McKinney Avenue, Suite 1500, Dallas, Texas 75201.

	The following table lists the Company’s primary operating subsidiaries and their reportable operating segment:

	Subsidiary	Operating Segment
	ARB, Inc. (“ARB”)	West Construction Services
	ARB Structures, Inc.	West Construction Services
	Q3 Contracting, Inc. (“Q3C”); acquired 2012	West Construction Services
	Rockford Corporation (“Rockford”)	West Construction Services
	Stellaris, LLC.	West Construction Services
	OnQuest, Inc.	Engineering
	OnQuest, Canada, ULC (Born Heaters Canada, ULC prior to 2013)	Engineering
	Cardinal Contractors, Inc.	East Construction Services
	Force Specialty Services, Inc. (“FSSI”); acquired 2013	East Construction Services
	James Construction Group, LLC (“JCG”)	East Construction Services
	Sprint Pipeline Services, L.P. (“Sprint”); acquired 2012	East Construction Services
	Silva Group (“Silva”); acquired 2012	East Construction Services
	The Saxon Group (“Saxon”); acquired 2012	East Construction Services

	The Company is a party to the Blythe Power Constructors joint venture (“Blythe”) for the installation of a parabolic trough solar field and steam generation system in California.

	Unless specifically noted otherwise, as used throughout these consolidated financial statements, “Primoris”, “the Company”, “we”, “our”, “us” or “its” refers to the business, operations and financial results of the Company and its wholly-owned subsidiaries.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2013
Basis of Presentation	'
Basis of Presentation	'
	Note 2—Basis of Presentation

	Interim consolidated financial statements— The interim condensed consolidated financial statements for the three-month and nine-month periods ended September 30, 2013 and 2012 have been prepared in accordance with Rule 10-01 of Regulation S-X of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). As such, certain disclosures, which would substantially duplicate the disclosures contained in the Company’s Annual Report on Form 10-K, filed on March 7, 2013, which contains the Company’s audited consolidated financial statements for the year ended December 31, 2012, have been omitted.

	This Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2013 (the “Third Quarter 2013 Report”) should be read in concert with the Company’s most recent Annual Report on form 10-K. The interim financial information is unaudited. In the opinion of management, the unaudited information includes all adjustments (consisting of normal recurring adjustments) necessary for the fair presentation of the interim financial information.

	Revenue recognition

	Fixed-price contracts — Historically, a substantial portion of the Company’s revenue has been generated under fixed-price contracts. For fixed-price contracts, the Company recognizes revenues using the percentage-of-completion method, which may result in uneven and irregular results. In the percentage-of-completion method, estimated revenues and resulting contract income are calculated based on the total costs incurred to date as a percentage of total estimated costs. If an estimate of total contract cost indicates a loss on a contract, the projected loss is recognized in full at the time of the estimate. The loss amount is recognized as an “accrued loss provision” and is included in the accrued expenses and other liabilities amount on the balance sheet. As the percentage-of-completion method is used to calculate revenues, the accrued loss provision is changed so that the gross profit for the contract is zero.

	Unforeseen events and circumstances can alter the estimate of the costs and potential profit associated with a particular contract. Total estimated costs, and thus contract revenues and income, can be impacted by changes in productivity, scheduling, the unit cost of labor, subcontracts, materials and equipment. Additionally, external factors such as weather, client needs, client delays in providing permits and approvals, labor availability, governmental regulation and politics may affect the progress of a project’s completion and thus the timing of revenue recognition. To the extent that original cost estimates are modified, estimated costs to complete increase, delivery schedules are delayed, or progress under a contract is otherwise impeded, cash flow, revenue recognition and profitability from a particular contract may be adversely affected.

	Other contract forms — The Company also uses unit-price, time and material, and cost reimbursable plus fee contracts. For these jobs, revenue is recognized based on contractual terms. For example, time and material contract revenues are recognized based on purchasing and employee time records. Similarly, unit price contracts recognize revenue based on completion of specific units at a specified unit price.

	For all of its contracts, the Company includes any provision for estimated losses on uncompleted contracts in accrued expenses. Changes in job performance, job conditions and estimated profitability, including those arising from final contract settlements, may result in revisions to costs and income. These revisions are recognized in the period in which the revisions are identified.

	The caption “Costs and estimated earnings in excess of billings” represents unbilled receivables which arise when revenues have been recorded but the amount will not be billed until a later date. Balances represent: (a) unbilled amounts arising from the use of the percentage-of-completion method of accounting which may not be billed under the terms of the contract until a later date, (b) incurred costs to be billed under cost reimbursement type contracts, or (c) amounts arising from routine lags in billing. For those contracts in which billings exceed contract revenues recognized to date, the excess amounts are included in the caption “Billings in excess of costs and estimated earnings”.

	The Company considers unapproved change orders to be contract variations for which it has customer approval for a change in scope but for which it does not have an agreed upon price change. Costs associated with unapproved change orders are included in the estimated cost to complete the contracts and are treated as project costs as incurred. The Company recognizes revenue equal to costs incurred on unapproved change orders when realization of price approval is probable. Unapproved change orders involve the use of estimates, and it is reasonably possible that revisions to the estimated costs and recoverable amounts may be required in future reporting periods to reflect changes in estimates or final agreements with customers.

	The Company considers claims to be amounts it seeks, or will seek, to collect from customers or others for customer-caused changes in contract specifications or design, or other customer-related causes of unanticipated additional contract costs on which there is no agreement with customers on both scope and price changes. Claims are included in the calculation of revenues when realization is probable and amounts can be reliably determined. Revenues in excess of contract costs incurred on claims are recognized when the amounts have been agreed upon with the customer. Revenue in excess of contract costs from claims is recognized when agreement is reached with customers as to the value of the claims, which in some instances may not occur until after completion of work under the contract. Costs associated with claims are included in the estimated costs to complete the contracts and are treated as project costs when incurred.

	In accordance with applicable terms of certain construction contracts, retainage amounts may be withheld by customers until completion and acceptance of the project. Some payments of the retainage may not be received for a significant period after completion of our portion of a project. In some jurisdictions, retainage amounts are deposited into an escrow account.

	Significant revision in contract estimate— As previously discussed, revenue recognition is based on the percentage-of-completion method for firm fixed-price contracts. Under this method, the costs incurred to date as a percentage of total estimated costs are used to calculate revenue. Total estimated costs, and thus contract revenues and margin, are impacted by many factors which can cause significant changes in estimates during the life cycle of a project.

	For projects that were in process in the prior year, but are either completed or continue to be in process during the current year, there can be a difference in revenues and profits recognized to the prior year, had current year estimates of costs to complete been known in the prior year.

	Customer Concentration — The Company operates in multiple industry segments encompassing the construction of commercial, industrial and public works infrastructure assets throughout the United States. Typically, the top ten customers in any one calendar year generate revenues in excess of 50% of total revenues and consist of a different group of customers in each year.

	During the three months and nine months ending September 30, 2013, revenues generated by the top ten customers were $274 million and $717 million, respectively, which represented 49.7% and 51.0%, respectively, of total revenues during the periods. During the three and nine month periods ending September 30, 2013, a large gas and electric utility represented 8.8% and 8.3%, respectively, of total revenues and a large pipeline company represented 9.7% and 6.8%, respectively, of total revenues.

	During the three and nine months ending September 30, 2012, revenues generated by the top ten customers were $243.6 million and $607.8 million, respectively, which represented 56.4% and 57.3%, respectively, of total revenues during the periods. During the three and nine month periods ending September 30, 2012, the Louisiana Department of Transportation represented 11.9% and 12.7%, respectively, of total revenues and a large gas and electric utility represented 16.1% and 13.6%, respectively, of total revenues.

	At September 30, 2013, approximately 13.1% of the Company’s accounts receivable were due from one customer, and that customer provided 7.4% of the Company’s revenues for the nine months ended September 30, 2013. At September 30, 2012, approximately 10.8% of the Company’s accounts receivable were due from one customer, and that customer provided 13.6% of the Company’s revenues for the nine months ended September 30, 2012.

	Multiemployer Plans— Various subsidiaries in the West Construction Services segment are signatories to collective bargaining agreements. These agreements require that the Company participate in and contribute to a number of multiemployer benefit plans for its union employees at rates determined by the agreements. The trustees for each multiemployer plan determine the eligibility and allocations of contributions and benefit amounts, determine the types of benefits and administer the plan. Federal law requires that if the Company were to withdraw from an agreement, it will incur a withdrawal obligation. The potential withdrawal obligation may be significant. Any withdrawal liability would be recorded when it is probable that a liability exists and can be reasonably estimated, in accordance with generally accepted accounting principles (“GAAP”). In November 2011, the Company withdrew from the Central States Southeast and Southwest Areas Pension Fund multiemployer pension plan. The Company has no plans to withdraw from any other agreements. See Note 19 — Commitments and Contingencies.

	Inventory and uninstalled contract materials — Inventory consists of expendable construction materials and small tools that will be used in construction projects and is valued at the lower of cost, using first-in, first-out method, or market. Uninstalled contract materials include certain job specific materials not yet installed which are valued using the specific identification method relating the cost incurred to a specific project.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	9 Months Ended
Recent Accounting Pronouncements	Sep. 30, 2013
Recent Accounting Pronouncements	'
Recent Accounting Pronouncements	'
	Note 3—Recent Accounting Pronouncements

	In January 2013, the FASB issued ASU 2013-01, which clarifies which instruments and transactions are subject to the offsetting disclosure requirements established by ASU 2011-11 , “Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities” . The ASU was effective for the fiscal years and interim periods beginning January 1, 2013. Retrospective application is required for any period presented that begins before the entity’s initial application of the new requirements. The adoption of this guidance did not have a material impact on the Company’s financial statements.

	In February 2013, the FASB issued ASU 2013-04, “Liabilities (Topic 405): Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation Is Fixed at the Reporting Date (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2013-04”). ASU 2013-04 provides guidance for the recognition, measurement, and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation within the scope of this guidance is fixed at the reporting date. This ASU is an update to FASB ASC Topic 405, “Liabilities”. The amendments in this ASU are effective for fiscal years, and interim periods, beginning after December 15, 2013. The adoption of this guidance is not expected to have a material impact on the Company’s financial statements.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2013
Fair Value Measurements	'
Fair Value Measurements	'
	Note 4—Fair Value Measurements

	ASC Topic 820, “Fair Value Measurements and Disclosures”, defines fair value in GAAP, establishes a framework for measuring fair value and requires certain disclosures about fair value measurements. ASC Topic 820 requires that certain financial assets and financial liabilities be re-measured and reported at fair value each reporting period and that other non-financial assets and liabilities be re-measured and reported at fair value on a non-recurring basis.

	ASC Topic 820 also establishes three reporting levels for fair value measurements. Fair values determined by Level 1 use quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair values determined by Level 2 inputs use data points that are observable such as quoted prices, interest rates and yield curves. Fair values determined by Level 3 inputs are “unobservable data points” for an asset or liability and include situations where there is little, if any, market activity for the asset or liability.

	The following table presents, for each of the fair value hierarchy levels identified under ASC Topic 820, the Company’s financial assets and liabilities that are required to be measured at fair value at September 30, 2013 and December 31, 2012:

					Fair Value Measurements at Reporting Date
		Amount			Quoted Prices		Significant	Significant
		Recorded			in Active Markets		Other	Unobservable
		on Balance			for Identical Assets		Observable	Inputs
		Sheet			(Level 1)		Inputs	(Level 3)
							(Level 2)
	Assets as of September 30, 2013:
	Cash and cash equivalents	$	174,034		$	174,034	—	—
	Short-term investments	$	3,179		$	3,179	—	—
	Liabilities as of September 30, 2013:
	Contingent consideration	$	14,846		—		—	$	14,846

	Assets as of December 31, 2012:
	Cash and cash equivalents	$	157,551		$	157,551	—	—
	Short-term investments	$	3,441		$	3,441	—	—
	Liabilities as of December 31, 2012:
	Contingent consideration	$	23,431		—		—	$	23,431

	Short-term investments consist primarily of Certificates of Deposit (“CDs”) purchased through the CDARS (Certificate of Deposit Account Registry Service) process and U.S. Treasury bills with various financial institutions that are backed by the federal government.

	Other financial instruments of the Company not listed in the table consist of accounts receivable, accounts payable and certain accrued liabilities. These financial instruments generally approximate fair value based on their short-term nature. The carrying value of the Company’s long-term debt approximates fair value based on comparison with current prevailing market rates for loans of similar risks and maturities.

	The following table provides changes to the Company’s contingent consideration liability Level 3 fair value measurements during the nine months ended September 30, 2013:

	Contingent Consideration
	Balance at December 31, 2012	$	23,431
	Additions:
	FSSI acquisition on March 11, 2013	702
	Change in fair value of contingent consideration	1,613
	Reductions:
	Payment to Rockford sellers	(6,900		)
	Payment to Sprint sellers	(4,000		)
	Balance at September 30, 2013	$	14,846

	On a quarterly basis, the Company assesses the estimated fair value of the contractual obligation to pay the contingent consideration and any changes in estimated fair value are recorded as other non-operating expense or income in the Company’s statement of operations. Fluctuations in the fair value of contingent consideration are impacted by two unobservable inputs, management’s estimate of the probability (which range from 33% to 100%) of the acquired company meeting the contractual operating performance target and the estimated discount rate (a rate that approximates the Company’s cost of capital). Significant changes in either of those inputs in isolation would result in a significantly different fair value measurement. Generally, a change in the assumption of the probability of meeting the performance target is accompanied by a directionally similar change in the fair value of contingent consideration liability, whereas a change in assumption of the estimated discount rate is accompanied by a directionally opposite change in the fair value of contingent consideration liability.

Accounts_Receivable

Accounts Receivable	9 Months Ended
	Sep. 30, 2013
Accounts Receivable	'
Accounts Receivable	'
	Note 5—Accounts Receivable

	The following is a summary of the Company’s accounts receivable:

		September 30,		December 31,
		2013		2012

	Contracts receivable, net of allowance for doubtful accounts of $535 at September 30, 2013 and $432 at December 31, 2012	$	235,302	$	227,548
	Retention	48,768		39,710
		284,070		267,258
	Other accounts receivable	427		837
		$	284,497	$	268,095

Costs_and_Estimated_Earnings_o

Costs and Estimated Earnings on Uncompleted Contracts	9 Months Ended
	Sep. 30, 2013
Costs and Estimated Earnings on Uncompleted Contracts	'
Costs and Estimated Earnings on Uncompleted Contracts	'
	Note 6—Costs and Estimated Earnings on Uncompleted Contracts

	Costs and estimated earnings on uncompleted contracts consist of the following at:

		September 30,			December 31,
		2013			2012

	Costs incurred on uncompleted contracts	$	4,256,810		$	3,882,968
	Reserve for estimated losses on uncompleted contracts	2,018			764
	Gross profit recognized	516,451			448,928
		4,775,279			4,332,660
	Less: billings to date	(4,842,309		)	(4,449,851		)
		$	(67,030	)	$	(117,191	)

	This amount is included in the accompanying consolidated balance sheet under the following captions:

		September 30,			December 31,
		2013			2012

	Costs and estimated earnings in excess of billings	$	80,434		$	41,701
	Billings in excess of costs and estimated earnings	(147,464		)	(158,892		)
		$	(67,030	)	$	(117,191	)

Equity_Method_Investments

Equity Method Investments	9 Months Ended
Equity Method Investments	Sep. 30, 2013
Equity Method Investments.	'
Equity Method Investments	'
	Note 7—Equity Method Investments

	WesPac Energy LLC and WesPac Midstream LLC

	On July 1, 2010, the Company acquired a 50% membership interest in WesPac Energy LLC, a Nevada limited liability company (“WesPac”), from Kealine Holdings, LLC (“Kealine”), a Nevada limited liability company. Kealine held the remaining 50% membership interest in WesPac. WesPac developed pipeline and terminal projects in the United States, Canada and Mexico.

	On September 30, 2013, WesPac, Kealine and the Company entered into a contribution agreement (the “Agreement”) with Highstar Capital IV, LP (“Highstar”), to form a new entity, WesPac Midstream LLC, a Delaware limited liability company (“WesPac-Midstream”), owned collectively by Highstar, Kealine and the Company. WesPac contributed certain project assets to WesPac-Midstream. Highstar contributed $6.1 million in cash for an 85% ownership interest in certain developmental projects. Of this amount, $3.04 million was distributed to the Company and accounted for as a reduction of the carrying value of the WesPac investment. Highstar also obtained a 75% interest in two of WesPac-Midstream’s more mature projects. Highstar may make additional payments to Kealine and the Company for the two projects contingent on completion of certain milestones as follows:

	1. When the first project reaches “commercial acceptance” (as that term is defined in the Agreement), a payment of $4.5 million will be made ($2.25 million to the Company), and an additional payment of $4.5 million when the project goes into production ($2.25 million to the Company).

	2. If the second project successfully reaches “commercial acceptance” prior to January 31, 2014, a payment of $4.5 million ($2.25 million to the Company) will be made and a similar payment when the project goes into production. If “commercial acceptance” is not received prior to July 1, 2014, no contingent payments will be made for this project.

	Highstar will fund WesPac-Midstream’s operations over the next two years. The Company is not required to fund any of WesPac-Midstream’s activities and retains one of five board seats.

	During the third quarter 2013 and prior to the Agreement, WesPac recorded a third quarter loss of $0.2 million and the Company recorded its 50% share of the loss of $0.1 million. After recording the loss, the carrying value of the WesPac investment prior to the sale to Highstar, was $11.5 million.

	In July 2010, the Company recorded a $5 million amount greater than its pro-rata share of the WesPac equity as part of its original investment (“basis difference”). In December 2011, as a result of certain events impacting WesPac, the Company recorded a reduction of $1.7 million of its $5 million basis difference. As a result of the Agreement, the Company eliminated the remaining basis difference of $3.25 million to recognize an other than temporary decrease in the value of its basis difference. The non-cash impairment charge was recorded as a Selling, General and Administrative expense. The Company’s remaining $4.76 million investment represents the Company’s pro-rata equity ownership in both the WesPac and WesPac-Midstream entities.

	The following is a summary of the financial position and results as of and for the periods ended:

			September 30,			December 31,
			2013			2012

	WesPac & WesPac-Midstream
	Balance sheet data
	Assets		$	18,856		$	16,896
	Liabilities		1,067			1,063
	Net assets		$	17,789		$	15,833
	Company’s equity investment		$	4,757		$	11,463

			Three months ended September 30,						Nine months ended September 30,
			2013			2012			2013			2012

	Earnings data:
	Revenue		$	10		$	—		$	99		$	511
	Expenses		$	235		$	358		$	754		$	1,002
	Earnings before taxes		$	(225	)	$	(358	)	$	(655	)	$	(491	)
	Company’s equity in earnings		$	(113	)	$	(178	)	$	(328	)	$	(245	)

	St.—Bernard Levee Partners

	The Company purchased a 30% interest in St.—Bernard Levee Partners (“Bernard”) in 2009 for $300 and accounts for this investment using the equity method. Bernard engaged in construction activities in Louisiana, and all work was completed in January 2013. The Company’s share of Bernard distributions for the nine months ended September 30, 2013 and 2012, was $145 and $1,260, respectively. The following is a summary of the financial position and results as of and for the periods ended:

			September 30,			December 31,
			2013			2012

	St. — Bernard Levee Partners
	Balance sheet data
	Assets		$	22		$	592
	Liabilities		22			86
	Net assets		$	—		$	506
	Company’s equity investment		$	—		$	150

			Three months ended September 30,						Nine months ended September 30,
			2013			2012			2013			2012

	Earnings data:
	Revenue		$	—		$	36		$	—		$	3,970
	Expenses		$	—		$	(36	)	$	16		$	162
	Earnings before taxes		$	—		$	72		$	(16	)	$	3,808
	Company’s equity in earnings		$	—		$	19		$	(5	)	$	1,140

	Alvah, Inc.

As part of the acquisition of Q3C, the Company acquired a 49% membership interest in Alvah, Inc., a California corporation (“Alvah”). Alvah is engaged in electrical contracting activities, primarily in Northern California and worked as a subcontractor for ARB both prior to and subsequent to the Q3C acquisition. In December 2012, the company received $98 from a distribution by Alvah. During the three and nine months ending September 30, 2013, payments made by ARB to Alvah were $2,154 and $5,064, respectively, and payments made by Q3C were $2 and $214, respectively. For the same periods in the prior year, ARB made payments of $1,609 and $3,762, respectively and Q3C made payments of $120 and $353, respectively.

The following is a summary of the financial position and results as of and for the period ended:

		September 30,			December 31,
		2013			2012

Balance sheet data
Assets		$	3,849		$	2,177
Liabilities		1,677			1,208
Net assets		$	2,172		$	969
Company’s equity investment in venture		$	1,789		$	1,200

		Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012

Earnings data:
Revenue		$	4,824		$	—		$	10,832		$	—
Expenses		$	4,185		$	—		$	9,630		$	—
Earnings after taxes		$	639		$	—		$	1,202		$	—
Company’s equity in earnings		$	313		$	—		$	589		$	—

Because Alvah was not acquired until November 2012, no activity is shown for the prior year.

Business_Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2013
Business Combinations	'
Business Combinations	'
	Note 8 — Business Combinations

	2013 Acquisition - FSSI

	On March 11, 2013, the Company’s subsidiary, Primoris Energy Services (“PES”), purchased the assets of Force Specialty Services Inc. (“FSSI”) which specializes in turn-around work at refineries and chemical plants in the Gulf Coast area. Based in the greater Houston, Texas area, FSSI’s location provides a presence and convenient access to refineries in south Texas, the Houston ship channel and Louisiana.

	The fair value of the consideration for the acquisition was $2,377. Consideration consisted of cash totaling $1,675, of which $1,025 was paid at closing and $650 was paid in the second quarter 2013. The agreement provides for three future potential payments, contingent upon FSSI meeting certain operating performance targets for the remainder of calendar year 2013 and calendar years 2014 and 2015.

	The contingent consideration is as follows: (1) $500 in cash for the achievement of pretax income of at least $553 for the remainder of the year ending December 31, 2013; (2) a payment of $500 in cash if pretax income for the year 2014 is at least $2,502; and (3), a payment of $500 in cash if pretax income for the year 2015 is at least $4,227. The estimated fair value of the potential contingent consideration on the acquisition date was $702 and at September 30, 2013 was $741.

	The purchase agreement also included a provision that PES make an up-front payment of $1,000 for a five-year employment, non-competition and non-solicitation agreement with a key employee. If the employee terminates his employment or violates the agreement prior to the end of the five-year period, he is required to repay the unamortized amount of the $1,000 payment. This agreement has been accounted for as a prepaid asset and is being amortized equally over the five-year period.

	At closing the Company received $302 in small tools inventory, $448 in property, plant and equipment, and recorded accounts payable of $1,060.

	The acquisition was accounted for using the acquisition method of accounting. The assets acquired and liabilities assumed were measured at their estimated fair value at the acquisition date Since its March 11, 2013 acquisition date, FSSI contributed revenues of $670 and $4,143 and gross profit of $14 and $325, for the three and nine months ended September 30, 2013, respectively.

	During the second quarter 2013, the Company finalized its estimates of the fair value of the contingent consideration, intangible assets and goodwill for the acquisition. The final revision resulted in a change from the estimated values recorded at March 31, 2013, including a decrease in the fair value of the contingent consideration of $136, increases in intangible assets of $800 and a decrease of $936 for goodwill

	The customer relationships were valued at $950 utilizing the “excess earnings method” of the income approach. The estimated discounted cash flows associated with existing customers and projects were based on historical and market participant data. Such discounted cash flows were net of fair market returns on the various tangible and intangible assets that are necessary to realize the potential cash flows.

	The fair value of the tradename of $550 was determined based on the “relief from royalty” method. A royalty rate was selected based on consideration of several factors, including external research of third party tradename licensing agreements and their royalty rate levels, and management estimates. The useful life was estimated at five years based on management’s expectation for continuing value of the tradename in the future.

	The fair value for the non-compete agreement of $100 was based on a discounted “income approach” model, including estimated financial results with and without the non-compete agreement in place. The agreement was analyzed based on the potential impact of competition that certain individuals could have on the financial results, assuming the agreement was not in place. An estimate of the probability of competition was applied and the results were compared to a similar model assuming the agreement was in place.

	Goodwill of $1,087 largely consists of expected benefits from the greater presence and convenient access to south Texas, the Houston ship channel and Louisiana and FSSI’s expertise in turn-around work for refineries and chemical plants. Goodwill also includes the value of the assembled workforce of the FSSI business. Based on the current tax treatment, goodwill and other intangible assets will be deductible for income tax purposes over a fifteen-year period.

	2012 Acquisition - Sprint Pipeline Services, L.P.

	The March 12, 2012 acquisition of Sprint was accounted for using the acquisition method of accounting. The fair value of the consideration totaled $28,377, which included cash payments of $21,197, Company stock valued at $980 (or 62,052 shares of restricted common stock) and contingent consideration of $6,200.

	The contingent consideration was as follows: if income before interest, taxes, depreciation and amortization (“EBITDA”) for 2012, as defined in the purchase agreement, was at least $7,000, we would pay $4,000 in cash to the sellers. The earnout target was achieved in 2012 and was paid in April 2013.

	The 2013 earnout target provides for an additional cash payment of $4,000 to the sellers if 2013 EBITDA is at least $7,750. The estimated fair value of the 2013 contingent consideration as of the acquisition date was $2,745 and at September 30, 2013 and December 31, 2012, the estimated fair value of the contingent consideration was $3,300 and $3,020, respectively.

	2012 Acquisition - Silva Companies

	The May 30, 2012 acquisition of Silva was accounted for using the acquisition method of accounting. The fair value of the consideration was $14,090.

	2012 Acquisition - The Saxon Group

	The September 28, 2012 acquisition of Saxon was accounted for using the acquisition method of accounting. The fair value of the consideration was $550 in cash, payment of a banknote for $2,429, and contingent consideration valued at $1,950 for total consideration of $4,929.

	The contingent consideration included an earnout where the Company would pay $2,500 to the sellers, contingent upon Saxon meeting one of the following two targets: (1) EBITDA for the fifteen month period ending December 31, 2013 of at least $4,000 or; (2) EBITDA for the twenty-one month period ending September 30, 2014 of at least $4,750. The estimated fair value of the contingent consideration on the acquisition date was $1,950. The estimated fair value of the contingent consideration was $2,269 and $2,028 at September 30, 2013 and December 31, 2012, respectively.

	2012 Acquisition — Q3 Contracting

	Using the acquisition method of accounting, the fair value of the consideration for the November 17, 2012 acquisition of Q3C totaled $56,592. At closing we made a cash payment of $48,116 and recorded a contingent earnout with a fair value of $7,448 and a liability for a future payment of $430 in Company common stock.

	The contingent earnout requires the Company to pay additional cash to the sellers, contingent on Q3C meeting certain EBITDA targets (as that term is defined in the stock purchase agreement). The targets are as follows:

	1. For the period November 18, 2012 through December 31, 2013, if EBITDA is at least $17,700, the Company will pay an additional $3,750. The payment amount increases by $1,250, to $5,000, if EBITDA exceeds $19,000.

	2. For calendar year 2014, if EBITDA is at least $19,000, the Company will pay an additional $3,750. The payment amount increases by $1,250, to $5,000, if EBITDA exceeds $22,000.

	As of the purchase date, the estimated fair value of the contingent consideration was $7,448. The fair value estimate is based on management’s evaluation of the probability of Q3C meeting the financial performance targets for the two periods, discounted at the Company’s estimated average cost of capital. The estimated fair value at September 30, 2013 and December 31, 2012 was $8,536 and $7,490, respectively (which includes the expectation that the 2013 target, item 1 above, will be met, with the fair value of $5,000 at September 30, 2013).

	In January 2013, we issued 29,273 shares of unregistered stock. In August 2013, we paid $598 in cash to the sellers as part of tax-related elections that were made under the terms of the purchase agreement.

	During the third quarter of 2013, the Company finalized its estimate of the fair value of the acquired assets and liabilities for the acquisition, resulting in no change to the initial estimate. Additionally, under the purchase agreement, the Company made a final true-up of the purchase amount during the third quarter 2013, resulting in an additional payment to the sellers of $598. This increased goodwill as of September 30, 2013, an increase in the original estimated goodwill value that had been recorded at December 31, 2012, March 31, 2013 and June 30, 2013.

	Summary of Cash Paid for Acquisitions for the nine months ended September 30, 2013 and 2012

	The following table summarizes the cash paid for acquisitions for the nine months ended September 30, 2013 and 2012. The Q3C acquisition was made on November 17, 2012 and included a cash payment of $48,116. The Company made an additional post-closing payment to the sellers in August 2013, which is included below:

		Nine Months ended September 30,
		2013		2012

Sprint — Purchased March 12, 2012		$	—	$	21,197
Silva — purchased May 30, 2012		—		13,934
Saxon — purchased September 28, 2012		—		2,979
FSSI — purchased March 11, 2013		1,675		—
Additional cash paid August 2013 — Q3C — purchased November 17, 2012		598		—
		$	2,273	$	38,110

Supplemental Unaudited Pro Forma Information for the three and nine months ended September 30, 2013 and 2012

In accordance with ASC Topic 805 we are combining the pro forma information for the FSSI, Sprint, Silva, Saxon and Q3C acquisitions (“the Acquisitions”). The following pro forma information for the three and nine months ended September 30, 2013 and 2012 presents the combined results of operations of the Acquisitions combined, as if the Acquisitions had each occurred at the beginning of 2012. The supplemental pro forma information has been adjusted to include:

· the pro forma impact of amortization of intangible assets and depreciation of property, plant and equipment, based on the purchase price allocations;

· the pro forma impact of the expense associated with the amortization of the discount for the fair value of the contingent consideration for potential earnout liabilities that may be achieved in 2013 for the Sprint and FSSI acquisitions and 2013 or 2014 for the Saxon, Q3C and FSSI acquisitions;

· the pro forma tax effect of both the income before income taxes and the pro forma adjustments, calculated using a tax rate of 39.0% for the three and nine months ended September 30, 2012 and the same periods in 2013; and

· the pro forma increase in weighted average shares outstanding including 62,052 unregistered shares of common stock issued as part of the Sprint acquisition and 29,273 shares of unregistered common stock issued as part of the Q3C acquisition.

The pro forma results are presented for illustrative purposes only and are not necessarily indicative of, or intended to represent, the results that would have been achieved had the Acquisitions been completed on January 1, 2012. For example, the pro forma results do not reflect any operating efficiencies and associated cost savings that the Company might have achieved with respect to the combined companies.

		Three months				Nine months
		ended September 30,				ended September 30,
		2013		2012		2013		2012

Revenues		551,333		476,570		1,409,140		1,192,167
Income before provision for income taxes		37,268		31,967		79,283		65,395
Net income attributable to Primoris		21,845		19,379		47,109		39,848

Weighted average common shares outstanding:
Basic		51,568		51,427		51,530		51,433
Diluted		51,671		51,433		51,594		51,448

Earnings per share:
Basic		$	0.42	$	0.38	$	0.91	$	0.77
Diluted		$	0.42	$	0.38	$	0.91	$	0.77

Intangible_Assets

Intangible Assets	9 Months Ended
Intangible Assets	Sep. 30, 2013
Intangible Assets	'
Intangible Assets	'
	Note 9—Intangible Assets

	At September 30, 2013 and December 31, 2012, intangible assets totaled $48,002 and $51,978, respectively, net of amortization. The September 30, 2013 balance includes the effect of the FSSI acquisition (See Note 8). The table below summarizes the intangible asset categories, amounts and the average amortization periods, which are generally on a straight-line basis, as follows:

		Amortization		September 30,		December 31,
		Period		2013		2012
	Tradename	3 to 10 years		$	21,808	$	23,586
	Non-compete agreements	2 to 5 years		$	2,991	$	4,130
	Customer relationships	5 to 15 years		$	23,203	$	24,212
	Backlog	0.75 years		$	—	$	50
	Total			$	48,002	$	51,978

	Amortization expense of intangible assets was $1,891 and $1,476 for the three months ended September 30, 2013 and 2012, respectively, and amortization expense for the nine months ended September 30, 2013 and 2012 was $5,576 and $4,669, respectively. Estimated future amortization expense for intangible assets is as follows:

	For the Years Ending	Estimated
	December 31,	Intangible
		Amortization
		Expense
	2013 (remaining three months)	$	1,891
	2014	7,454
	2015	6,404
	2016	6,029
	2017	5,909
	Thereafter	20,315
		$	48,002

Accounts_Payable_and_Accrued_L

Accounts Payable and Accrued Liabilities	9 Months Ended
	Sep. 30, 2013
Accounts Payable and Accrued Liabilities	'
Accounts Payable and Accrued Liabilities	'
	Note 10—Accounts Payable and Accrued Liabilities

	At September 30, 2013 and December 31, 2012, accounts payable included retention amounts of approximately $8,359 and $15,946, respectively. These amounts are due to subcontractors but have been retained pending contract completion and customer acceptance of jobs.

	The following is a summary of accrued expenses and other current liabilities at:

		September 30,		December 31,
		2013		2012

	Payroll and related employee benefits	$	51,354	$	33,086
	Insurance, including self-insurance reserves	35,233		22,982
	Reserve for estimated losses on uncompleted contracts	2,018		764
	Corporate income taxes and other taxes	2,396		3,779
	Accrued overhead cost	1,326		2,007
	Other	9,554		13,534
		$	101,881	$	76,152

Credit_Arrangements

Credit Arrangements	9 Months Ended
Credit Arrangements	Sep. 30, 2013
Credit Arrangements	'
Credit Arrangements	'
	Note 11—Credit Arrangements

	Revolving Credit Facility

	As of September 30, 2013, the Company had a revolving credit facility (the “Credit Agreement”). The Credit Agreement was entered into by and among the Company, The PrivateBank and Trust Company, as administrative agent (the “Administrative Agent”) and co-lead arranger, The Bank of the West, as co-lead arranger, and IBERIABANK Corporation (the “Lenders”). The Credit Agreement is a $75 million revolving credit facility whereby the lenders agree to make loans on a revolving basis from time to time and to issue letters of credit for up to the $75 million committed amount. The Credit Agreement also provides for an incremental facility of up to $50 million. The termination date of the Credit Agreement is December 28, 2017.

	The principal amount of any loans under the Credit Agreement will bear interest at either: (i) LIBOR plus an applicable margin as specified in the Credit Agreement (based on the Company’s senior debt to EBITDA ratio), or (ii) the Base Rate (which is the greater of (a) the Federal Funds Rate plus 0.5% or (b) the prime rate as announced by the Administrative Agent). Quarterly non-use fees, letter of credit fees and administrative agent fees are payable at rates specified in the Credit Agreement.

	The principal amount of any loan drawn under the Credit Agreement may be prepaid in whole or in part, with a minimum prepayment of $5 million, at any time, potentially subject to make-whole provisions.

	The Credit Agreement includes customary restrictive covenants for facilities of this type, as discussed below.

	Commercial letters of credit were $4,808 at September 30, 2013 and $4,808 at December 31, 2012. Other than commercial letters of credit, there were no borrowings under this line of credit during the nine months ended September 30, 2013, leaving available borrowing capacity at $70,192 at September 30, 2013.

	At the execution of the Credit Agreement, the previous Loan and Security Agreement dated October 29, 2009, as amended, between the Company and The Private Bank and Trust Company (the “PrivateBank Agreement”), was terminated. There were no borrowings outstanding at the time of the termination and all outstanding letters of credit were transferred to the Credit Agreement.

	Senior Secured Notes and Shelf Agreement

	On December 28, 2012, the Company entered into a $50 million Senior Secured Notes purchase (“Senior Notes”) and a $25 million private shelf agreement (the “Notes Agreement”) by and among the Company, The Prudential Investment Management, Inc. and certain Prudential affiliates (the “Noteholders”).

	The Senior Notes amount was funded on December 28, 2012. The Senior Notes are due December 28, 2022 and bear interest at an annual rate of 3.65%, paid quarterly in arrears. Annual principal payments of $7.1 million are required from December 28, 2016 through December 28, 2021 with a final payment due on December 28, 2022. The principal amount may be prepaid, with a minimum prepayment of $5 million, at any time, subject to make-whole provisions.

	The Notes Agreement provided for the issuance of notes of up to $25 million, prior to December 28, 2016. On July 25, 2013, the Company drew the full $25 million available under the Notes Agreement. The notes are due July 25, 2023 and bear interest at an annual rate of 3.85% paid quarterly in arrears. Seven annual principal payments of $3.6 million are required from July 25, 2017 with a final payment due on July 25, 2023.

	All loans made under both the Credit Agreement and the Notes Agreement are secured by our assets, including, among others, our cash, inventory, goods, equipment (excluding equipment subject to permitted liens) and accounts receivable. All of our domestic subsidiaries have issued joint and several guaranties in favor of the Lenders and Noteholders for all amounts under the Credit Agreement and Notes Agreement.

	Both the Credit Agreement and the Notes Agreement contain various restrictive and financial covenants including among others, minimum tangible net worth, senior debt/EBITDA ratio, debt service coverage requirements and a minimum balance for unencumbered net book value for fixed assets. In addition, the agreements include restrictions on investments, change of control provisions and provisions in the event the Company disposes more than 20% of its total assets.

	The Company was in compliance with the covenants for the Credit Agreement and Notes Agreement at September 30, 2013.

	Canadian Credit Facility

	The Company has a credit facility for $10,000 in Canadian dollars with a Canadian bank for purposes of issuing commercial letters of credit in Canada. The credit facility has an annual renewal and provides for the issuance of commercial letters of credit for a term of up to five years. The facility provides for an annual fee of 1% for any issued and outstanding commercial letters of credit. Letters of credit can be denominated in either Canadian or U.S. dollars. At September 30, 2013 and December 31, 2012, letters of credit outstanding totaled $3,410 and $1,364 in Canadian dollars, respectively. At September 30, 2013, the available borrowing capacity was $6,590 in Canadian dollars. The credit facility contains a working capital restrictive covenant for our Canadian subsidiary, OnQuest Canada, ULC. At September 30, 2013, OnQuest Canada, ULC was in compliance with the covenant.

	Subordinated Promissory Notes

	Subordinated Promissory Note — Rockford. In connection with the 2010 acquisition of Rockford, the Company executed an unsecured promissory note with an initial principal amount of $16,712. In December 2012, the subordinated note was deemed paid.

	Subordinated Promissory Note — JCG. In connection with the 2009 acquisition of JCG, the Company executed an unsecured promissory note on December 18, 2009 with an initial principal amount of $53,500. The JCG note was paid in full on March 12, 2012.

Noncontrolling_Interests

Noncontrolling Interests	9 Months Ended
	Sep. 30, 2013
Noncontrolling Interests	'
Noncontrolling Interests	'
	Note 12 — Noncontrolling Interests

	The Company applies the provisions of ASC Topic 810-10-45, which establishes accounting and reporting standards for ownership interests of parties other than the Company in subsidiaries, such as joint ventures and partnerships.

	The Company determined that the Blythe joint venture was a variable interest entity (“VIE”) and that the Company was the primary beneficiary as a result of its significant influence over the joint venture operations.

	The Blythe joint venture operating activities are included in the Company’s consolidated statements of income as follows:

		Three months				Nine months
		ended September 30,				ended September 30,
		2013		2012		2013	2012

	Revenues	15,468		7,750		47,371	13,164
	Net income attributable to noncontrolling interests	1,348		432		1,947	600

	Since Blythe is a partnership, no tax effect was recognized for the income. Blythe made a $2.5 million distribution to the noncontrolling interests and $2.5 million distribution to the Company during the nine months ended September 30, 2013. There were no distributions made in the prior year, and there were no capital contributions made during the nine months ended September 30, 2013.

	The carrying value of the assets and liabilities associated with the operations of the Blythe joint venture are included in the Company’s consolidated balance sheets as follows:

		September 30,			December 31,
		2013			2012

	Cash	$	1,793		$	3,565
	Accounts receivable	8,448			8,843
	Current liabilities	8,318			9,379


	The net assets of the joint venture are restricted for use by the project and are not available for general operations of the Company.

Contingent_Earnout_Liabilities

Contingent Earnout Liabilities	9 Months Ended
Contingent Earnout Liabilities	Sep. 30, 2013
Contingent Earnout Liabilities	'
Contingent Earnout Liabilities	'
	Note 13 — Contingent Earnout Liabilities

	As part of the Rockford acquisition in November 2010, the Company agreed to issue additional cash and common stock to the sellers, contingent upon Rockford meeting certain operating performance targets The final contingent earnout for 2012 was achieved and in April 2013, the Company made a $6,900 cash payment.

	The Company has recorded additional contingent earnout consideration liabilities related to the acquisitions of FSSI, Sprint, Saxon and Q3C as discussed in Note 8 — Business Combinations.

Related_Party_Transactions

Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2013
Related Party Transactions	'
Related Party Transactions	'
	Note 14—Related Party Transactions

	Primoris has entered into leasing transactions with Stockdale Investment Group, Inc. (“SIGI”). Brian Pratt, our Chief Executive Officer, President and Chairman of the Board of Directors and our largest stockholder, holds a majority interest and is the chairman, president and chief executive officer and a director of SIGI. John M. Perisich, our Executive Vice President and General Counsel, is secretary of SIGI.

	Primoris leases properties from SIGI at the following locations:

	1. Bakersfield, California (lease expires October 2022)
	2. Pittsburg, California (lease expires April 2023)
	3. San Dimas, California (lease expires March 2019)
	4. Pasadena, Texas (leases expire in July 2019 and 2021)

	During the nine months ended September 30, 2013 and 2012, the Company paid $688 and $695, respectively, in lease payments to SIGI for the use of these properties.

	The Company entered into a $6.1 million agreement in 2010 to construct a wastewater facility for Pluris, LLC, a private company in which Brian Pratt holds the majority interest. The transaction was reviewed and approved by the Audit Committee of the Board of Directors of the Company. The project was substantially completed in December 2011. The Company recognized no revenues or profits in 2013 and recognized revenues of $362 for the nine months ended September 30, 2012, at normal margins.

	Primoris leases a property from Roger Newnham, a former owner and current manager of our subsidiary, OnQuest Canada, ULC. The property is located in Calgary, Canada. During the nine months ended September 30, 2013 and 2012, Primoris paid $223 and $212, respectively, in lease payments. The current term of the lease is through December 31, 2014.

	Primoris leases a property from Lemmie Rockford, one of the Rockford sellers, which commenced November 1, 2011. The property is located in Toledo, Washington. During the nine months ended September 30, 2013 and 2012, Primoris paid $68 and $68, respectively, in lease payments. The lease expires in January 2015.

	As a result of the November 2012 acquisition of Q3C, the Company became party to leased property from Quality RE Partners, owned by three of the Q3C selling shareholders, of whom two are current employees, including Jay Osborn, President of Q3C. The property is located in Little Canada, Minnesota. During the nine months ended September 30, 2013, the Company paid $198, in lease payments to Quality RE Partners for the use of this property. The lease commenced October 28, 2012 and expires in October 2022.

	As discussed in Note 7— “Equity Method Investments”, the Company owns several non-consolidated investments and has recognized revenues on work performed by the Company for those joint ventures.

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
Stock-Based Compensation	Sep. 30, 2013
Stock-Based Compensation	'
Stock-Based Compensation	'
	Note 15—Stock-Based Compensation

	On May 3, 2013, the Board of Directors granted 100,000 Restricted Stock Units (“Units”) under the 2013 Equity Incentive Plan (the “2013 Plan”). The Units vest over a service period of four equal installments in 2014 through 2017, subject to earlier acceleration, termination, cancellation or forfeiture as provided in the underlying award agreement. Each Unit represents the right to receive one share of the Company’s common stock when vested.

	The fair value of the Units was based on the closing market price of our common stock on the day prior to the date of the grant, or $21.98 per Unit. Stock compensation expense for the Units is being amortized using the straight-line method over the service vesting period. For the three and nine months ended September 30, 2013 the Company recognized $138 and $229, respectively, in compensation expense. At September 30, 2013, approximately $1.97 million of unrecognized compensation expense remains for the Units which will be recognized over a period of 3.6 years.

	Vested Units accrue “Dividend Equivalents” (as defined in the 2013 Plan) which will be accrued as additional Units. At September 30, 2013, there were no accrued Dividend Equivalent Units.

Income_Taxes

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2013
Income Taxes	'
Income Taxes	'
	Note 16—Income Taxes

	The effective tax rate on income before taxes and noncontrolling interests for the nine months ended September 30, 2013 is 38.13%. The effective tax rate for income attributable to Primoris is 39.09%. The rate differs from the U.S. federal statutory rate of 35% due primarily to state income taxes, the “Domestic Production Activity Deduction” and nondeductible meals and incidental per diems common in the construction industry.

	To determine its quarterly provision for income taxes, the Company uses an estimated annual effective tax rate, which is based on expected annual income, statutory tax rates and tax planning opportunities available in the various jurisdictions in which the Company operates. Certain significant or unusual items are separately recognized in the quarter in which they occur and can be a source of variability in the effective tax rate from quarter to quarter. The Company recognizes interest and penalties related to uncertain tax positions, if any, as an income tax expense.

	Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences of temporary differences between the financial reporting basis and tax basis of the Company’s assets and liabilities. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment date.

	In September 2012, the Internal Revenue Service (“IRS”) concluded an examination of our federal income tax returns for 2008 and 2009, which did not have a material impact on our financial statements. In the third quarter of 2013, the IRS initiated an examination of our federal income tax return for 2011. The tax years 2010 through 2012 remain open to examination by the IRS. The statute of limitations of state and foreign jurisdictions vary generally between 3 to 5 years. Accordingly, the tax years 2008 through 2012 generally remain open to examination by the other major taxing jurisdictions in which the Company operates.

Dividends_and_Earnings_Per_Sha

Dividends and Earnings Per Share	9 Months Ended
	Sep. 30, 2013
Dividends and Earnings Per Share	'
Dividends and Earnings Per Share	'
	Note 17—Dividends and Earnings Per Share

	The Company has paid or declared cash dividends during 2013 as follows:

	· On March 5, 2013, the Company declared a cash dividend of $0.03 per common share, payable to stockholders of record on March 29, 2013. The dividend, totaling $1,547, was paid on April 15, 2013.
	· On May 3, 2013, the Company declared a cash dividend of $0.035 per common share, payable to stockholders of record on June 28, 2013. The dividend, totaling $1,805, was paid on July 15, 2013.
	· On August 2, 2013, the Company declared a cash dividend of $0.035 per common share, payable to stockholders of record on September 30, 2013. The dividend, totaling $1,805, was paid on October 15, 2013.

	The table below presents the computation of basic and diluted earnings per share for the three and nine months ended September 30, 2013 and 2012:

		Three months				Nine months
		ended September 30,				ended September 30,
		2013		2012		2013		2012
	Numerator:
	Net income attributable to Primoris	$	21,845	$	17,516	$	47,179	$	39,735
	Denominator (shares in thousands):
	Weighted average shares for computation of basic earnings per share	51,568		51,398		51,529		51,387
	Dilutive effect of shares issued to independent directors	3		6		10		15
	Dilutive effect of shares issued as part of Q3C acquisition	—		—		1		—
	Dilutive effect of unvested restricted stock units	100		—		55		—
	Weighted average shares for computation of diluted earnings per share	51,671		51,404		51,595		51,402

	Earnings per share:
	Basic earnings per share	$	0.42	$	0.34	$	0.92	$	0.77
	Diluted earnings per share	$	0.42	$	0.34	$	0.91	$	0.77

Stockholders_Equity

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2013
Stockholders' Equity	'
Stockholders' Equity	'
	Note 18—Stockholders’ Equity

	Common stock — In March 2013, the Company received $1,455 for 131,989 shares of common stock issued, under a purchase arrangement within the Company’s Long-Term Incentive Plan (“LTI Plan”) for managers and executives. The LTI Plan allows participants to use a portion of their annual bonus amount to purchase Company common stock at a discount from the market price. The shares purchased in March 2013 were for bonus amounts earned in 2012 and were calculated at 75% of the average market closing price of December 2012. In March 2012, the Company received $1,240 for 111,790 shares of common stock issued under the LTI Plan for bonus amounts earned in the prior year.

	In March 2013 and in August 2013, the Company issued 12,480 shares and 9,110 shares, respectively, of common stock as part of the quarterly compensation of the non-employee members of the Board of Directors.

	As part of the acquisition of Q3C, the Company issued 29,273 unregistered shares of stock on January 7, 2013. The shares were issued based on the average December 2012 closing prices, or $14.69 per share for a total value of $430.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2013
Commitments and Contingencies.	'
Commitments and Contingencies	'
	Note 19—Commitments and Contingencies

	Leases— The Company leases certain property and equipment under non-cancellable operating leases which expire at various dates through 2019. The leases require the Company to pay all taxes, insurance, maintenance and utilities and are classified as operating leases in accordance with ASC Topic 840 “Leases”.

	Total lease expense during the three and nine months ended September 30, 2013 was $3,566 and $11,111, respectively, compared to $2,629 and $7,388 for the same periods in 2012. The amounts for the three and nine months ended September 30, 2013 included lease payments made to related parties of $379 and $1,176, respectively, and $327 and $975 for the three and nine months ended September 30, 2012, respectively.

	Letters of credit— At September 30, 2013, the Company had letters of credit outstanding of $8,123 and at December 31, 2012, the Company had letters of credit outstanding of $6,168. The outstanding amounts include the U.S. dollar equivalents for letters of credit issued in Canadian dollars.

	Litigation — On February 7, 2012, the Company was sued in an action entitled North Texas Tollway Authority, Plaintiff v. James Construction Group, LLC, and KBR, Inc., Defendants, v. Reinforced Earth Company, Third-Party Defendant (the “Lawsuit”). The Lawsuit was brought in the District Court of Collin County, Texas, 401st Judicial District, Cause No. 401-01747-2012. In the Lawsuit, the North Texas Tollway Authority (“NTTA”) is alleging damages to a road and retaining wall that were constructed in 1999 on the George Bush Turnpike near Dallas, Texas, due to negligent construction by JCG. The Lawsuit claims that the cost to repair the retaining wall was approximately $5.4 million. The NTTA also alleges that six other walls constructed on the project by JCG could have the same potential exposure to failure. The Company has denied any liability, but has tendered the claim to its insurance carriers and has cross-complained against its engineering subcontractor for potential design liability. The extent of insurance coverage by the carriers of the Company and its subcontractor are undetermined at this time. The Company has investigated all potential causes of the alleged loss, including design liabilities of the owner, owner’s engineers and/or the Company’s subcontractor. To date, mediation efforts have not been successful, and a jury trial is likely to be scheduled for 2014. While the Company will vigorously defend the claims, after discussion with its legal counsel, the Company recorded an accrual amount for this issue.

	The Company is subject to other claims and legal proceedings arising out of its business. Management believes that the Company has meritorious defenses to such claims. Although management is unable to ascertain the ultimate outcome of such matters, after review and consultation with counsel and taking into consideration relevant insurance coverage and related deductibles, management believes that the outcome of these matters will not have a materially adverse effect on the consolidated financial position of the Company.

	Bonding— At September 30, 2013 and December 31, 2012, the Company had bid and completion bonds issued and outstanding totaling approximately $1,449,158 and $1,298,589, respectively.

	Withdrawal liability for multiemployer pension plan— In November 2011, Rockford and ARB, along with other members of the Pipe Line Contractors Association (“PLCA”), withdrew from the Central States Southeast and Southwest Areas Pension Fund multiemployer pension plan (the “Plan”). The Company withdrew from the Plan in order to mitigate its liability in connection with the Plan, which is significantly underfunded. The Company recorded a liability of $7,500 based on information provided by the Plan. However, the Plan has asserted that the PLCA members did not affect a proper withdrawal in 2011. The Company believes that a legally effective withdrawal occurred in November 2011 and has recorded the withdrawal liability on that basis. If the Plan were to prevail in its assertion and the withdrawal of the Company were deemed to occur after 2011, the amount of any withdrawal liability could increase.

	Prior to its acquisition, Q3C had also withdrawn from the Plan. In November 2012, Q3C estimated a withdrawal liability of $85. In the first quarter of 2013, the Plan asserted that the liability was $119. Without agreeing to the amount, Q3C is making payments toward the liability amount.

	Contingent Consideration— Earnouts related to acquisitions are discussed in Note 8 — Business Combinations and Note 13 — Contingent Earnout Liabilities.

Reportable_Operating_Segments

Reportable Operating Segments	9 Months Ended
Reportable Operating Segments	Sep. 30, 2013
Reportable Operating Segments	'
Reportable Operating Segments	'
	Note 20—Reportable Operating Segments

	The Company segregates its business into three operating segments: the East Construction Services (“East”) segment, the West Construction Services (“West”) segment and the Engineering segment.

	The East segment includes the JCG construction business, located primarily in the southeastern United States and the businesses located in the Gulf Coast region of the United States, including Cardinal Contractors, Inc. The segment also includes the operating results relating to the acquisitions of Sprint, Silva and Saxon in 2012 and FSSI in 2013.

	The West segment includes the construction services performed by ARB, ARB Structures, Inc., Rockford, Alaska Continental Pipeline, Inc., All Day Electric Company, Inc., Primoris Renewables, Inc., Juniper Rock, Inc. and Stellaris, LLC. This segment also includes the operating results of Q3C acquired in November 2012. While most of the entities perform work primarily in California, Rockford operates throughout the United States and Q3C operates in the upper Midwest United States. The Blythe joint venture is also included as a part of the segment.

	The Engineering segment includes the results of OnQuest, Inc. and OnQuest Canada, ULC.

	All intersegment revenues and gross profit, which were immaterial, have been eliminated in the following tables.

	Segment Revenues

	Revenue by segment for the three months ended September 30, 2013 and 2012 were as follows:

			For the three months ended September 30,
			2013					2012
	Segment		Revenue			% of		Revenue			% of
						Segment					Segment
						Revenue					Revenue

	East		$	178,716		32.4	%	$	181,260		42	%
	West		362,362			65.7	%	242,033			56	%
	Engineering		10,255			1.9	%	8,549			2	%
	Total		$	551,333		100	%	$	431,842		100	%

	Revenue by segment for the nine months ended September 30, 2013 and 2012 were as follows:

			For the nine months ended September 30,
			2013					2012
	Segment		Revenue			% of		Revenue			% of
						Segment					Segment
						Revenue					Revenue

	East		$	544,325		38.7	%	$	459,167		43.3	%
	West		828,242			58.9	%	567,351			53.5	%
	Engineering		33,774			2.4	%	34,333			3.2	%
	Total		$	1,406,341		100	%	$	1,060,851		100	%

	Segment Gross Profit

	Gross profit by segment for the three months ended September 30, 2013 and 2012 were as follows:

			For the three months ended September 30,
			2013					2012
	Segment		Gross			% of		Gross			% of
			Profit			Segment		Profit			Segment
						Revenue					Revenue

	East		$	10,600		5.9	%	$	18,664		10.3	%
	West		62,520			17.3	%	35,602			14.7	%
	Engineering		2,345			22.9	%	2,025			23.7	%
	Total		$	75,465		13.7	%	$	56,291		13	%

	Gross profit by segment for the nine months ended September 30, 2013 and 2012 were as follows:

			For the nine months ended September 30,
			2013					2012
	Segment		Gross			% of		Gross			% of
			Profit			Segment		Profit			Segment
						Revenue					Revenue

East		$	40,810		7.5	%	$	47,442		10.3	%
West		133,195			16.1	%	84,297			14.9	%
Engineering		7,093			21	%	6,152			17.9	%
Total		$	181,098		12.9	%	$	137,891		13	%

Segment Goodwill

The following presents the amount of goodwill recorded by segment at September 30, 2013 and at December 31, 2012.

Segment		September 30,			December 31,
Segment		2013			2012

East		$	70,946		$	69,859
West		45,239			44,641
Engineering		2,441			2,441
Total		$	118,626		$	116,941

Geographic Region — Revenues and Total Assets

Revenue and total assets by geographic area for the nine months ended September 30, 2013 and 2012 were as follows:

		Revenues
		For the nine months ended September 30,
		2013					2012					Total Assets
Country:		Revenue			% of		Revenue			% of		September 30,		December 31,
Country:		Revenue			Revenue		Revenue			Revenue		2013		2012

United States		$	1,393,837		99.1	%	$	1,053,547		99.3	%	$	1,007,980	$	920,872
Non-United States		12,504			0.9		7,304			0.7		11,097		10,335
Total		$	1,406,341		100	%	$	1,060,851		100	%	$	1,019,077	$	931,207

All non-United States revenue were generated in the Engineering segment. For the table above, revenues generated by OnQuest Canada, ULC, were used to determine non-United States revenues.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
Basis of Presentation (Policies)	Sep. 30, 2013
Basis of Presentation	'
Revenue recognition	'
	Revenue recognition

	Fixed-price contracts — Historically, a substantial portion of the Company’s revenue has been generated under fixed-price contracts. For fixed-price contracts, the Company recognizes revenues using the percentage-of-completion method, which may result in uneven and irregular results. In the percentage-of-completion method, estimated revenues and resulting contract income are calculated based on the total costs incurred to date as a percentage of total estimated costs. If an estimate of total contract cost indicates a loss on a contract, the projected loss is recognized in full at the time of the estimate. The loss amount is recognized as an “accrued loss provision” and is included in the accrued expenses and other liabilities amount on the balance sheet. As the percentage-of-completion method is used to calculate revenues, the accrued loss provision is changed so that the gross profit for the contract is zero.

	Unforeseen events and circumstances can alter the estimate of the costs and potential profit associated with a particular contract. Total estimated costs, and thus contract revenues and income, can be impacted by changes in productivity, scheduling, the unit cost of labor, subcontracts, materials and equipment. Additionally, external factors such as weather, client needs, client delays in providing permits and approvals, labor availability, governmental regulation and politics may affect the progress of a project’s completion and thus the timing of revenue recognition. To the extent that original cost estimates are modified, estimated costs to complete increase, delivery schedules are delayed, or progress under a contract is otherwise impeded, cash flow, revenue recognition and profitability from a particular contract may be adversely affected.

	Other contract forms — The Company also uses unit-price, time and material, and cost reimbursable plus fee contracts. For these jobs, revenue is recognized based on contractual terms. For example, time and material contract revenues are recognized based on purchasing and employee time records. Similarly, unit price contracts recognize revenue based on completion of specific units at a specified unit price.

	For all of its contracts, the Company includes any provision for estimated losses on uncompleted contracts in accrued expenses. Changes in job performance, job conditions and estimated profitability, including those arising from final contract settlements, may result in revisions to costs and income. These revisions are recognized in the period in which the revisions are identified.

	The caption “Costs and estimated earnings in excess of billings” represents unbilled receivables which arise when revenues have been recorded but the amount will not be billed until a later date. Balances represent: (a) unbilled amounts arising from the use of the percentage-of-completion method of accounting which may not be billed under the terms of the contract until a later date, (b) incurred costs to be billed under cost reimbursement type contracts, or (c) amounts arising from routine lags in billing. For those contracts in which billings exceed contract revenues recognized to date, the excess amounts are included in the caption “Billings in excess of costs and estimated earnings”.

	The Company considers unapproved change orders to be contract variations for which it has customer approval for a change in scope but for which it does not have an agreed upon price change. Costs associated with unapproved change orders are included in the estimated cost to complete the contracts and are treated as project costs as incurred. The Company recognizes revenue equal to costs incurred on unapproved change orders when realization of price approval is probable. Unapproved change orders involve the use of estimates, and it is reasonably possible that revisions to the estimated costs and recoverable amounts may be required in future reporting periods to reflect changes in estimates or final agreements with customers.

	The Company considers claims to be amounts it seeks, or will seek, to collect from customers or others for customer-caused changes in contract specifications or design, or other customer-related causes of unanticipated additional contract costs on which there is no agreement with customers on both scope and price changes. Claims are included in the calculation of revenues when realization is probable and amounts can be reliably determined. Revenues in excess of contract costs incurred on claims are recognized when the amounts have been agreed upon with the customer. Revenue in excess of contract costs from claims is recognized when agreement is reached with customers as to the value of the claims, which in some instances may not occur until after completion of work under the contract. Costs associated with claims are included in the estimated costs to complete the contracts and are treated as project costs when incurred.

	In accordance with applicable terms of certain construction contracts, retainage amounts may be withheld by customers until completion and acceptance of the project. Some payments of the retainage may not be received for a significant period after completion of our portion of a project. In some jurisdictions, retainage amounts are deposited into an escrow account.

Significant revision in contract estimate	'
	Significant revision in contract estimate— As previously discussed, revenue recognition is based on the percentage-of-completion method for firm fixed-price contracts. Under this method, the costs incurred to date as a percentage of total estimated costs are used to calculate revenue. Total estimated costs, and thus contract revenues and margin, are impacted by many factors which can cause significant changes in estimates during the life cycle of a project.

	For projects that were in process in the prior year, but are either completed or continue to be in process during the current year, there can be a difference in revenues and profits recognized to the prior year, had current year estimates of costs to complete been known in the prior year.

Customer Concentration	'
	Customer Concentration — The Company operates in multiple industry segments encompassing the construction of commercial, industrial and public works infrastructure assets throughout the United States. Typically, the top ten customers in any one calendar year generate revenues in excess of 50% of total revenues and consist of a different group of customers in each year.

	During the three months and nine months ending September 30, 2013, revenues generated by the top ten customers were $274 million and $717 million, respectively, which represented 49.7% and 51.0%, respectively, of total revenues during the periods. During the three and nine month periods ending September 30, 2013, a large gas and electric utility represented 8.8% and 8.3%, respectively, of total revenues and a large pipeline company represented 9.7% and 6.8%, respectively, of total revenues.

	During the three and nine months ending September 30, 2012, revenues generated by the top ten customers were $243.6 million and $607.8 million, respectively, which represented 56.4% and 57.3%, respectively, of total revenues during the periods. During the three and nine month periods ending September 30, 2012, the Louisiana Department of Transportation represented 11.9% and 12.7%, respectively, of total revenues and a large gas and electric utility represented 16.1% and 13.6%, respectively, of total revenues.

	At September 30, 2013, approximately 13.1% of the Company’s accounts receivable were due from one customer, and that customer provided 7.4% of the Company’s revenues for the nine months ended September 30, 2013. At September 30, 2012, approximately 10.8% of the Company’s accounts receivable were due from one customer, and that customer provided 13.6% of the Company’s revenues for the nine months ended September 30, 2012.

Multiemployer Plans	'
	Multiemployer Plans— Various subsidiaries in the West Construction Services segment are signatories to collective bargaining agreements. These agreements require that the Company participate in and contribute to a number of multiemployer benefit plans for its union employees at rates determined by the agreements. The trustees for each multiemployer plan determine the eligibility and allocations of contributions and benefit amounts, determine the types of benefits and administer the plan. Federal law requires that if the Company were to withdraw from an agreement, it will incur a withdrawal obligation. The potential withdrawal obligation may be significant. Any withdrawal liability would be recorded when it is probable that a liability exists and can be reasonably estimated, in accordance with generally accepted accounting principles (“GAAP”). In November 2011, the Company withdrew from the Central States Southeast and Southwest Areas Pension Fund multiemployer pension plan. The Company has no plans to withdraw from any other agreements. See Note 19 — Commitments and Contingencies.

Inventory and uninstalled contract materials	'
	Inventory and uninstalled contract materials — Inventory consists of expendable construction materials and small tools that will be used in construction projects and is valued at the lower of cost, using first-in, first-out method, or market. Uninstalled contract materials include certain job specific materials not yet installed which are valued using the specific identification method relating the cost incurred to a specific project.

Nature_of_Business_Tables

Nature of Business (Tables)	9 Months Ended
Nature of Business (Tables)	Sep. 30, 2013
Nature of Business	'
Schedule of list of primary operating subsidiaries and their reportable operating segment	'


	Subsidiary	Operating Segment
	ARB, Inc. (“ARB”)	West Construction Services
	ARB Structures, Inc.	West Construction Services
	Q3 Contracting, Inc. (“Q3C”); acquired 2012	West Construction Services
	Rockford Corporation (“Rockford”)	West Construction Services
	Stellaris, LLC.	West Construction Services
	OnQuest, Inc.	Engineering
	OnQuest, Canada, ULC (Born Heaters Canada, ULC prior to 2013)	Engineering
	Cardinal Contractors, Inc.	East Construction Services
	Force Specialty Services, Inc. (“FSSI”); acquired 2013	East Construction Services
	James Construction Group, LLC (“JCG”)	East Construction Services
	Sprint Pipeline Services, L.P. (“Sprint”); acquired 2012	East Construction Services
	Silva Group (“Silva”); acquired 2012	East Construction Services
	The Saxon Group (“Saxon”); acquired 2012	East Construction Services

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2013
Fair Value Measurements	'
Schedule of financial assets and liabilities which are required to be measured at fair value	'


					Fair Value Measurements at Reporting Date
		Amount			Quoted Prices		Significant	Significant
		Recorded			in Active Markets		Other	Unobservable
		on Balance			for Identical Assets		Observable	Inputs
		Sheet			(Level 1)		Inputs	(Level 3)
							(Level 2)
	Assets as of September 30, 2013:
	Cash and cash equivalents	$	174,034		$	174,034	—	—
	Short-term investments	$	3,179		$	3,179	—	—
	Liabilities as of September 30, 2013:
	Contingent consideration	$	14,846		—		—	$	14,846

	Assets as of December 31, 2012:
	Cash and cash equivalents	$	157,551		$	157,551	—	—
	Short-term investments	$	3,441		$	3,441	—	—
	Liabilities as of December 31, 2012:
	Contingent consideration	$	23,431		—		—	$	23,431
Schedule of changes to the Company's contingent consideration liability Level 3 fair value measurements	'


	Contingent Consideration
	Balance at December 31, 2012	$	23,431
	Additions:
	FSSI acquisition on March 11, 2013	702
	Change in fair value of contingent consideration	1,613
	Reductions:
	Payment to Rockford sellers	(6,900		)
	Payment to Sprint sellers	(4,000		)
	Balance at September 30, 2013	$	14,846

Accounts_Receivable_Tables

Accounts Receivable (Tables)	9 Months Ended
	Sep. 30, 2013
Accounts Receivable	'
Summary of accounts receivable	'


		September 30,		December 31,
		2013		2012

	Contracts receivable, net of allowance for doubtful accounts of $535 at September 30, 2013 and $432 at December 31, 2012	$	235,302	$	227,548
	Retention	48,768		39,710
		284,070		267,258
	Other accounts receivable	427		837
		$	284,497	$	268,095

Costs_and_Estimated_Earnings_o1

Costs and Estimated Earnings on Uncompleted Contracts (Tables)	9 Months Ended
	Sep. 30, 2013
Costs and Estimated Earnings on Uncompleted Contracts	'
Schedule of costs and estimated earnings on uncompleted contracts	'


		September 30,			December 31,
		2013			2012

	Costs incurred on uncompleted contracts	$	4,256,810		$	3,882,968
	Reserve for estimated losses on uncompleted contracts	2,018			764
	Gross profit recognized	516,451			448,928
		4,775,279			4,332,660
	Less: billings to date	(4,842,309		)	(4,449,851		)
		$	(67,030	)	$	(117,191	)
Schedule of costs and estimated earnings on uncompleted contracts included in consolidated balance sheet	'


		September 30,			December 31,
		2013			2012

	Costs and estimated earnings in excess of billings	$	80,434		$	41,701
	Billings in excess of costs and estimated earnings	(147,464		)	(158,892		)
		$	(67,030	)	$	(117,191	)

Equity_Method_Investments_Tabl

Equity Method Investments (Tables)	9 Months Ended
Equity Method Investments (Tables)	Sep. 30, 2013
WesPac & WesPac-Midstream	'
Equity method investments	'
Summary of the financial position and results	'


		September 30,			December 31,
		2013			2012

	WesPac & WesPac-Midstream
	Balance sheet data
	Assets	$	18,856		$	16,896
	Liabilities	1,067			1,063
	Net assets	$	17,789		$	15,833
	Company’s equity investment	$	4,757		$	11,463

		Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012

	Earnings data:
	Revenue	$	10		$	—		$	99		$	511
	Expenses	$	235		$	358		$	754		$	1,002
	Earnings before taxes	$	(225	)	$	(358	)	$	(655	)	$	(491	)
	Company’s equity in earnings	$	(113	)	$	(178	)	$	(328	)	$	(245	)
Bernard	'
Equity method investments	'
Summary of the financial position and results	'


		September 30,			December 31,
		2013			2012

	St. — Bernard Levee Partners
	Balance sheet data
	Assets	$	22		$	592
	Liabilities	22			86
	Net assets	$	—		$	506
	Company’s equity investment	$	—		$	150

		Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012

	Earnings data:
	Revenue	$	—		$	36		$	—		$	3,970
	Expenses	$	—		$	(36	)	$	16		$	162
	Earnings before taxes	$	—		$	72		$	(16	)	$	3,808
	Company’s equity in earnings	$	—		$	19		$	(5	)	$	1,140
Alvah, Inc.	'
Equity method investments	'
Summary of the financial position and results	'


		September 30,			December 31,
		2013			2012

	Balance sheet data
	Assets	$	3,849		$	2,177
	Liabilities	1,677			1,208
	Net assets	$	2,172		$	969
	Company’s equity investment in venture	$	1,789		$	1,200

		Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012

	Earnings data:
	Revenue	$	4,824		$	—		$	10,832		$	—
	Expenses	$	4,185		$	—		$	9,630		$	—
	Earnings after taxes	$	639		$	—		$	1,202		$	—
	Company’s equity in earnings	$	313		$	—		$	589		$	—

Business_Combinations_Tables

Business Combinations (Tables)	9 Months Ended
Business Combinations (Tables)	Sep. 30, 2013
Business Combinations	'
Summary of the cash paid for acquisitions	'


		Nine Months ended September 30,
		2013		2012

	Sprint — Purchased March 12, 2012	$	—	$	21,197
	Silva — purchased May 30, 2012	—		13,934
	Saxon — purchased September 28, 2012	—		2,979
	FSSI — purchased March 11, 2013	1,675		—
	Additional cash paid August 2013 — Q3C — purchased November 17, 2012	598		—
		$	2,273	$	38,110
Schedule of pro forma results	'


		Three months				Nine months
		ended September 30,				ended September 30,
		2013		2012		2013		2012

	Revenues	551,333		476,570		1,409,140		1,192,167
	Income before provision for income taxes	37,268		31,967		79,283		65,395
	Net income attributable to Primoris	21,845		19,379		47,109		39,848

	Weighted average common shares outstanding:
	Basic	51,568		51,427		51,530		51,433
	Diluted	51,671		51,433		51,594		51,448

	Earnings per share:
	Basic	$	0.42	$	0.38	$	0.91	$	0.77
	Diluted	$	0.42	$	0.38	$	0.91	$	0.77

Intangible_Assets_Tables

Intangible Assets (Tables)	9 Months Ended
Intangible Assets (Tables)	Sep. 30, 2013
Intangible Assets	'
Summary of intangible asset categories, amounts and the average amortization periods	'


		Amortization		September 30,		December 31,
		Period		2013		2012
	Tradename	3 to 10 years		$	21,808	$	23,586
	Non-compete agreements	2 to 5 years		$	2,991	$	4,130
	Customer relationships	5 to 15 years		$	23,203	$	24,212
	Backlog	0.75 years		$	—	$	50
	Total			$	48,002	$	51,978
Schedule of estimated future amortization expense for intangible assets	'


	For the Years Ending	Estimated
	December 31,	Intangible
		Amortization
		Expense
	2013 (remaining three months)	$	1,891
	2014	7,454
	2015	6,404
	2016	6,029
	2017	5,909
	Thereafter	20,315
		$	48,002

Accounts_Payable_and_Accrued_L1

Accounts Payable and Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2013
Accounts Payable and Accrued Liabilities	'
Summary of accrued expenses and other current liabilities	'


		September 30,		December 31,
		2013		2012

	Payroll and related employee benefits	$	51,354	$	33,086
	Insurance, including self-insurance reserves	35,233		22,982
	Reserve for estimated losses on uncompleted contracts	2,018		764
	Corporate income taxes and other taxes	2,396		3,779
	Accrued overhead cost	1,326		2,007
	Other	9,554		13,534
		$	101,881	$	76,152

Noncontrolling_Interests_Table

Noncontrolling Interests (Tables)	9 Months Ended
Noncontrolling Interests (Tables)	Sep. 30, 2013
Noncontrolling Interests	'
Schedule of the Blythe joint venture operating activities included in the Company's consolidated statements of income	'


		Three months				Nine months
		ended September 30,				ended September 30,
		2013		2012		2013	2012

	Revenues	15,468		7,750		47,371	13,164
	Net income attributable to noncontrolling interests	1,348		432		1,947	600
Schedule of the carrying value of the assets and liabilities associated with the operations of the Blythe joint venture included in the Company's consolidated balance sheets	'


		September 30,			December 31,
		2013			2012

	Cash	$	1,793		$	3,565
	Accounts receivable	8,448			8,843
	Current liabilities	8,318			9,379

Dividends_and_Earnings_Per_Sha1

Dividends and Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Dividends and Earnings Per Share	'
Schedule of computation of basic and diluted earnings per share	'


		Three months				Nine months
		ended September 30,				ended September 30,
		2013		2012		2013		2012
	Numerator:
	Net income attributable to Primoris	$	21,845	$	17,516	$	47,179	$	39,735
	Denominator (shares in thousands):
	Weighted average shares for computation of basic earnings per share	51,568		51,398		51,529		51,387
	Dilutive effect of shares issued to independent directors	3		6		10		15
	Dilutive effect of shares issued as part of Q3C acquisition	—		—		1		—
	Dilutive effect of unvested restricted stock units	100		—		55		—
	Weighted average shares for computation of diluted earnings per share	51,671		51,404		51,595		51,402

	Earnings per share:
	Basic earnings per share	$	0.42	$	0.34	$	0.92	$	0.77
	Diluted earnings per share	$	0.42	$	0.34	$	0.91	$	0.77

Reportable_Operating_Segments_

Reportable Operating Segments (Tables)	9 Months Ended
Reportable Operating Segments (Tables)	Sep. 30, 2013
Reportable Operating Segments	'
Schedule of revenue by segment	'
	Segment Revenues

	Revenue by segment for the three months ended September 30, 2013 and 2012 were as follows:

		For the three months ended September 30,
		2013				2012
	Segment	Revenue		% of		Revenue		% of
				Segment				Segment
				Revenue				Revenue

	East	$	178,716	32.4	%	$	181,260	42	%
	West	362,362		65.7	%	242,033		56	%
	Engineering	10,255		1.9	%	8,549		2	%
	Total	$	551,333	100	%	$	431,842	100	%

	Revenue by segment for the nine months ended September 30, 2013 and 2012 were as follows:

		For the nine months ended September 30,
		2013				2012
	Segment	Revenue		% of		Revenue		% of
				Segment				Segment
				Revenue				Revenue

	East	$	544,325	38.7	%	$	459,167	43.3	%
	West	828,242		58.9	%	567,351		53.5	%
	Engineering	33,774		2.4	%	34,333		3.2	%
	Total	$	1,406,341	100	%	$	1,060,851	100	%
Schedule of gross profit by segment	'
	Segment Gross Profit

	Gross profit by segment for the three months ended September 30, 2013 and 2012 were as follows:

		For the three months ended September 30,
		2013				2012
	Segment	Gross		% of		Gross		% of
		Profit		Segment		Profit		Segment
				Revenue				Revenue

	East	$	10,600	5.9	%	$	18,664	10.3	%
	West	62,520		17.3	%	35,602		14.7	%
	Engineering	2,345		22.9	%	2,025		23.7	%
	Total	$	75,465	13.7	%	$	56,291	13	%

	Gross profit by segment for the nine months ended September 30, 2013 and 2012 were as follows:

		For the nine months ended September 30,
		2013				2012
	Segment	Gross		% of		Gross		% of
		Profit		Segment		Profit		Segment
				Revenue				Revenue

	East	$	40,810	7.5	%	$	47,442	10.3	%
	West	133,195		16.1	%	84,297		14.9	%
	Engineering	7,093		21	%	6,152		17.9	%
	Total	$	181,098	12.9	%	$	137,891	13	%
Schedule of amount of goodwill recorded by segment	'
	Segment Goodwill

	The following presents the amount of goodwill recorded by segment at September 30, 2013 and at December 31, 2012.

	Segment	September 30,		December 31,
	Segment	2013		2012

	East	$	70,946	$	69,859
	West	45,239		44,641
	Engineering	2,441		2,441
	Total	$	118,626	$	116,941
Schedule of revenue and total assets by geographic area	'
	Geographic Region — Revenues and Total Assets

	Revenue and total assets by geographic area for the nine months ended September 30, 2013 and 2012 were as follows:

		Revenues
		For the nine months ended September 30,
		2013				2012				Total Assets
	Country:	Revenue		% of		Revenue		% of		September 30,		December 31,
	Country:	Revenue		Revenue		Revenue		Revenue		2013		2012

	United States	$	1,393,837	99.1	%	$	1,053,547	99.3	%	$	1,007,980	$	920,872
	Non-United States	12,504		0.9		7,304		0.7		11,097		10,335
	Total	$	1,406,341	100	%	$	1,060,851	100	%	$	1,019,077	$	931,207

Basis_of_Presentation_Details

Basis of Presentation (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Customer concentration	'	'	'	'
Revenues	$551,333	$431,842	$1,406,341	$1,060,851
Revenues \| Customer concentration \| Top ten customers	'	'	'	'
Customer concentration	'	'	'	'
Number of top customers	10	10	10	10
Number of calendar years in which top customers typically generate minimum specified percentage of revenue	'	'	1	'
Revenues	$274,000	$243,600	$717,000	$607,800
Percentage of concentration risk	49.70%	56.40%	51.00%	57.30%
Revenues \| Customer concentration \| Top ten customers \| Minimum	'	'	'	'
Customer concentration	'	'	'	'
Minimum percentage of revenues generated by top ten customers	'	'	50.00%	'
Revenues \| Customer concentration \| Large gas and electric utility	'	'	'	'
Customer concentration	'	'	'	'
Percentage of concentration risk	8.80%	16.10%	8.30%	13.60%
Revenues \| Customer concentration \| Large gas pipeline company	'	'	'	'
Customer concentration	'	'	'	'
Percentage of concentration risk	9.70%	'	6.80%	'
Revenues \| Customer concentration \| One customer	'	'	'	'
Customer concentration	'	'	'	'
Percentage of concentration risk	'	'	7.40%	13.60%
Revenues \| Customer concentration \| Louisiana Department of Transportation	'	'	'	'
Customer concentration	'	'	'	'
Percentage of concentration risk	'	11.90%	'	12.70%
Accounts receivable \| Customer concentration \| One customer	'	'	'	'
Customer concentration	'	'	'	'
Percentage of concentration risk	'	'	13.10%	10.80%

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets	'	'
Short-term investments	$3,179	$3,441
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)	'	'
Assets	'	'
Cash and cash equivalents	174,034	157,551
Short-term investments	3,179	3,441
Recurring \| Significant Unobservable Inputs (Level 3)	'	'
Liabilities	'	'
Contingent consideration	14,846	23,431
Recurring \| Amount Recorded on Balance Sheet	'	'
Assets	'	'
Cash and cash equivalents	174,034	157,551
Short-term investments	3,179	3,441
Liabilities	'	'
Contingent consideration	$14,846	$23,431

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (USD $)

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

In Thousands, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Mar. 11, 2013

Jun. 30, 2013

Sep. 30, 2013

Mar. 12, 2012

Sep. 30, 2012

Sep. 30, 2013

Mar. 11, 2013

Sep. 30, 2013

FSSI acquisition

Sprint sellers

Saxon Group

Contingent consideration

item

FSSI acquisition

Rockford sellers

Sprint sellers

Rollforward of contingent consideration liability level three fair value measurements

Balance at the beginning of the period

$23,431

Additions

702

Change in fair value of contingent consideration

-9,287

-2,489

1,613

Payments

-2,273

-38,110

-1,025

-650

-1,675

-21,197

-2,979

-6,900

-4,000

Balance at the end of the period

$14,846

Additional information

Number of unobservable inputs

Minimum probability of acquired entity meeting contractual operating performance target (as a percent)

33.00%

Maximum probability of acquired entity meeting contractual operating performance target (as a percent)

100.00%

Accounts_Receivable_Details

Accounts Receivable (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts Receivable	'	'
Contracts receivable, net of allowance for doubtful accounts	$235,302	$227,548
Retention	48,768	39,710
Contracts receivable and retention	284,070	267,258
Other accounts receivable	427	837
Accounts receivable, net	284,497	268,095
Allowance for doubtful accounts	$535	$432

Costs_and_Estimated_Earnings_o2

Costs and Estimated Earnings on Uncompleted Contracts (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Costs and Estimated Earnings on Uncompleted Contracts	'	'
Costs incurred on uncompleted contracts	$4,256,810	$3,882,968
Reserve for estimated losses on uncompleted contracts	2,018	764
Gross profit recognized	516,451	448,928
Costs and Estimated Earnings on Uncompleted Contracts	4,775,279	4,332,660
Less: billings to date	-4,842,309	-4,449,851
Net cost and estimated earnings in excess of billings	-67,030	-117,191
Amount included in consolidated balance sheet	'	'
Costs and estimated earnings in excess of billings	80,434	41,701
Billings in excess of costs and estimated earnings	-147,464	-158,892
Net cost and estimated earnings in excess of billings	($67,030)	($117,191)

Equity_Method_Investments_Deta

Equity Method Investments (Details) (USD $)

3 Months Ended

9 Months Ended

12 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Dec. 31, 2011

Sep. 30, 2013

Jul. 31, 2010

Jul. 01, 2010

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Dec. 31, 2009

Dec. 31, 2012

Sep. 30, 2013

Nov. 17, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

WesPac

WesPac & WesPac-Midstream

Bernard

Alvah, Inc.

WesPac-Midstream

Kealine

ARB

Q3C

item

Highstar

WesPac, Kealine and the Company

Company

Highstar

Developmental projects

Mature projects

First mature project

Second mature project

Developmental projects

First mature project

Second mature project

item

Equity method investments

Membership interest (as a percent)

50.00%

30.00%

49.00%

Project interest sold (as a percent)

85.00%

75.00%

Cash proceeds from sale of projects

$6,100,000

$3,040,000

Number of projects sold

Payment to be made by the counterparty to agreement upon the project reaching commercial acceptance stage

4,500,000

2,250,000

Payment to be made by the counterparty to agreement upon the project reaching production stage

4,500,000

2,250,000

Payment to be made by the counterparty to agreement, upon project not successfully reaching the commercial acceptance stage prior to July 1, 2014

Funding period

'2 years

Number of board seats retained by Company

Number of board seats

Basis difference between the entity's original investment and its pro-rata share of the investee equity prior to any impairment adjustment

3,250,000

5,000,000

Reduction recorded to recognize an estimate for an other than temporary decrease

3,250,000

1,700,000

Balance sheet data

Assets

18,856,000

16,896,000

22,000

592,000

2,177,000

3,849,000

Liabilities

1,067,000

1,063,000

22,000

86,000

1,208,000

1,677,000

Net assets

17,789,000

15,833,000

506,000

969,000

2,172,000

Company's equity investment

6,546,000

12,813,000

4,757,000

11,463,000

150,000

1,200,000

1,789,000

Earnings data:

Revenue

10,000

99,000

511,000

36,000

3,970,000

4,824,000

10,832,000

Expenses

235,000

358,000

754,000

1,002,000

-36,000

16,000

162,000

4,185,000

9,630,000

Earnings before taxes

-225,000

-358,000

-655,000

-491,000

72,000

-16,000

3,808,000

Earnings after taxes

639,000

1,202,000

Company's equity in earnings

113,000

-159,000

169,000

895,000

-113,000

-178,000

-328,000

-245,000

19,000

-5,000

1,140,000

313,000

589,000

Cost of investment

300,000

Share in distribution

3,186,000

1,260,000

145,000

1,260,000

98,000

Payments made to equity method investee

$2,154,000

$1,609,000

$5,064,000

$3,762,000

$2,000

$120,000

$214,000

$353,000

Business_Combinations_Details

Business Combinations (Details) (USD $)

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

0 Months Ended

In Thousands, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Mar. 11, 2013

Sep. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 11, 2013

Customer relationship

Tradename

Non-compete agreement

FSSI

Minimum

item

Revisions

2013 earnout target

2014 earnout target

2015 earnout target

Non-competition and non-solicitation agreement with a key employee

Customer relationship

Tradename

Non-compete agreement

Minimum

2013 Acquisition - FSSI

Total consideration

$2,377

Cash consideration

1,675

Cash paid for acquisitions

2,273

38,110

1,025

650

1,675

Number of future potential payments based on agreed upon contingencies

Contingent consideration in cash

500

Pretax income threshold for measuring financial performance

553

2,502

4,227

Contingent consideration

702

741

Up-front payment

1,000

Period of employment, non-competition and non-solicitation agreement with a key employee

'5 years

Intangible assets

1,000

950

550

100

Amortization period of agreement

'5 years

'3 years

'2 years

'5 years

Small tools inventory received in acquisition

302

Property, plant and equipment received in acquisition

448

Accounts payable received in acquisition

1,060

Revenues

670

4,143

Gross Profit

325

Decrease in the fair value of the contingent consideration

9,287

2,489

136

Increases in intangible assets

800

Decrease in goodwill

936

Estimated useful life of intangible assets

'5 years

Goodwill

$118,626

$116,941

$1,087

Amortization period of goodwill and other intangible assets for income tax purposes

'15 years

Business_Combinations_Details_

Business Combinations (Details 2) (USD $)	9 Months Ended		0 Months Ended	9 Months Ended			0 Months Ended				0 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Mar. 12, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 12, 2012	Mar. 12, 2012	Sep. 30, 2013	Dec. 31, 2012	Mar. 12, 2012	Mar. 12, 2012
			Sprint	Sprint	Sprint	Sprint	Sprint	Sprint	Sprint	Sprint	Sprint
						2012 earnout target	2012 earnout target	2013 earnout target	2013 earnout target	2013 earnout target	2013 earnout target
							Minimum				Minimum
2012 Acquisition - Sprint Pipeline Services, L.P.	'	'	'	'	'	'	'	'	'	'	'
Total consideration	'	'	$28,377	'	'	'	'	'	'	'	'
Cash paid for acquisitions	2,273	38,110	21,197	'	21,197	'	'	'	'	'	'
Company common stock as a part of consideration	'	'	980	'	'	'	'	'	'	'	'
Number of shares of common stock issued	'	'	62,052	62,052	'	'	'	'	'	'	'
Contingent consideration	'	'	6,200	'	'	'	'	3,300	3,020	2,745	'
Pretax income threshold for measuring financial performance	'	'	'	'	'	'	7,000	'	'	'	7,750
Contingent consideration in cash	'	'	'	'	'	$4,000	'	'	'	$4,000	'

Business_Combinations_Details_1

Business Combinations (Details 3) (Silva, USD $)	0 Months Ended
In Thousands, unless otherwise specified	30-May-12
Silva	'
2012 Acquisition - Silva Companies	'
Total consideration	$14,090

Business_Combinations_Details_2

Business Combinations (Details 4) (Saxon, USD $)	0 Months Ended
In Thousands, unless otherwise specified	Sep. 28, 2012	Sep. 30, 2013	Dec. 31, 2012
	item	Sep. 30, 2013	Dec. 31, 2012
2012 Acquisition - The Saxon Group	'	'	'
Cash consideration	$550	'	'
Bank note as part of consideration	2,429	'	'
Contingent consideration	1,950	2,269	2,028
Total consideration	4,929	'	'
Contingent consideration in cash	2,500	'	'
Number of targets for payment of contingent cash consideration	2	'	'
2013 earnout target	'	'	'
2012 Acquisition - The Saxon Group	'	'	'
EBITDA period	'15 months	'	'
2013 earnout target \| Minimum	'	'	'
2012 Acquisition - The Saxon Group	'	'	'
Pretax income threshold for measuring financial performance	4,000	'	'
2014 earnout target	'	'	'
2012 Acquisition - The Saxon Group	'	'	'
EBITDA period	'21 months	'	'
2014 earnout target \| Minimum	'	'	'
2012 Acquisition - The Saxon Group	'	'	'
Pretax income threshold for measuring financial performance	$4,750	'	'

Business_Combinations_Details_3

Business Combinations (Details 5) (USD $)

9 Months Ended

0 Months Ended

1 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

In Thousands, except Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Jan. 07, 2013

Nov. 17, 2012

Aug. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Nov. 17, 2012

Sep. 30, 2013

Q3C

Earnout target period from November 18, 2012 through December 31, 2013

2014 earnout target

Minimum

Maximum

Minimum

Maximum

2012 Acquisition - Q3 Contracting

Total consideration

$56,592

Cash paid for acquisitions

2,273

38,110

48,116

598

Contingent consideration

7,448

8,536

7,490

Company common stock as a part of consideration

430

Pretax income threshold for measuring financial performance

17,700

19,000

Contingent consideration in cash

3,750

Additional potential contingent consideration

1,250

5,000

1,250

5,000

EBITDA threshold for measuring financial performance, case two

$19,000

$22,000

Unregistered shares of common stock issued with an acquisition

29,273

Business_Combinations_Details_4

Business Combinations (Details 6) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

1 Months Ended

9 Months Ended

In Thousands, except Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Mar. 12, 2012

Sep. 30, 2013

Sep. 30, 2012

Mar. 11, 2013

Jun. 30, 2013

Sep. 30, 2013

Jan. 07, 2013

Nov. 17, 2012

Aug. 31, 2013

Sep. 30, 2013

Sprint

Silva

Saxon

FSSI

Q3C

Business combinations

Cash paid for acquisitions

$2,273

$38,110

$21,197

$13,934

$2,979

$1,025

$650

$1,675

$48,116

$598

Pro forma results

Pro forma tax rate used in calculating taxes on income from continuing operations (as a percent)

39.00%

Unregistered shares of common stock issued with an acquisition

62,052

29,273

Revenues

551,333

476,570

1,409,140

1,192,167

Income before provision for income taxes

37,268

31,967

79,283

65,395

Net income attributable to Primoris

$21,845

$19,379

$47,109

$39,848

Weighted average common shares outstanding:

Basic (in shares)

51,568

51,427

51,530

51,433

Diluted (in shares)

51,671

51,433

51,594

51,448

Earnings per share:

Basic (in dollars per share)

$0.42

$0.38

$0.91

$0.77

Diluted (in dollars per share)

$0.42

$0.38

$0.91

$0.77

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Intangible assets	'	'	'	'	'
Amortization expense of intangible assets	$1,891	$1,476	$5,576	$4,669	'
Estimated future amortization expense for intangible assets	'	'	'	'	'
2013 (remaining three months)	1,891	'	1,891	'	'
2014	7,454	'	7,454	'	'
2015	6,404	'	6,404	'	'
2016	6,029	'	6,029	'	'
2017	5,909	'	5,909	'	'
Thereafter	20,315	'	20,315	'	'
Total	48,002	'	48,002	'	51,978
Tradename	'	'	'	'	'
Estimated future amortization expense for intangible assets	'	'	'	'	'
Total	21,808	'	21,808	'	23,586
Tradename \| Minimum	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'3 years	'	'
Tradename \| Maximum	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'10 years	'	'
Non-compete agreements	'	'	'	'	'
Estimated future amortization expense for intangible assets	'	'	'	'	'
Total	2,991	'	2,991	'	4,130
Non-compete agreements \| Minimum	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'2 years	'	'
Non-compete agreements \| Maximum	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'5 years	'	'
Customer relationship	'	'	'	'	'
Estimated future amortization expense for intangible assets	'	'	'	'	'
Total	23,203	'	23,203	'	24,212
Customer relationship \| Minimum	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'5 years	'	'
Customer relationship \| Maximum	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'15 years	'	'
Backlog	'	'	'	'	'
Intangible assets	'	'	'	'	'
Amortization Period	'	'	'9 months	'	'
Estimated future amortization expense for intangible assets	'	'	'	'	'
Total	'	'	'	'	$50

Accounts_Payable_and_Accrued_L2

Accounts Payable and Accrued Liabilities (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts Payable and Accrued Liabilities	'	'
Retention amounts included in accounts payable	$8,359	$15,946
Accrued expenses and other current liabilities	'	'
Payroll and related employee benefits	51,354	33,086
Insurance, including self-insurance reserves	35,233	22,982
Reserve for estimated losses on uncompleted contracts	2,018	764
Corporate income taxes and other taxes	2,396	3,779
Accrued overhead cost	1,326	2,007
Other	9,554	13,534
Total accrued expenses and other current liabilities	$101,881	$76,152

Credit_Arrangements_Details

Credit Arrangements (Details)

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

Sep. 30, 2013

Dec. 28, 2012

Sep. 30, 2013

Jul. 25, 2013

Dec. 28, 2012

Sep. 30, 2013

Dec. 28, 2012

Dec. 31, 2010

Dec. 18, 2009

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Oct. 29, 2009

Senior Notes

Notes Agreement

Subordinated Promissory Note

Credit Agreement

Canadian Credit Facility

Agreement with Private Bank and Trust Company

USD ($)

Minimum

USD ($)

Minimum

Maximum

Rockford

James Construction Group LLC

LIBOR

Base rate

Federal funds rate

Prime rate

Minimum

Revolving line of credit

Commercial letters of credit

USD ($)

item

USD ($)

Minimum

USD ($)

CAD

Maximum

USD ($)

Credit arrangements

Maximum borrowing capacity

$75,000,000

10,000,000

Incremental maximum borrowing capacity

50,000,000

Variable rate basis

'LIBOR

'Base Rate

'Federal Funds Rate

'prime rate

Basis spread on variable rate (as a percent)

0.50%

Prepayment to be paid on debt

5,000,000

Interest rate (as a percent)

3.65%

3.85%

Restrictions on investments, change of control provisions and provisions as a percentage of total assets to be disposed off

20.00%

Total commercial letters of credit outstanding

4,808,000

3,410,000

1,364,000

Available borrowing capacity

70,192,000

6,590,000

Borrowings to be incurred prior to December 28, 2016

25,000,000

Borrowings outstanding

Term of credit facility

'5 years

Annual fee (as a percent)

1.00%

Required principal payment

7,100,000

3,600,000

Initial principal amount

$50,000,000

$25,000,000

$16,712,000

$53,500,000

Number of annual principal payments

Noncontrolling_Interests_Detai

Noncontrolling Interests (Details) (USD $)	3 Months Ended		9 Months Ended
Noncontrolling Interests (Details) (USD $)	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Noncontrolling Interests	'	'	'	'	'
Revenues	$551,333,000	$431,842,000	$1,406,341,000	$1,060,851,000	'
Net income attributable to noncontrolling interests	1,348,000	432,000	1,947,000	600,000	'
Tax effect on income recognized	14,075,000	10,965,000	30,272,000	24,875,000	'
Accounts receivable	284,497,000	'	284,497,000	'	268,095,000
Current liabilities	410,633,000	'	410,633,000	'	420,669,000
Blythe joint venture \| Primary beneficiary	'	'	'	'	'
Noncontrolling Interests	'	'	'	'	'
Revenues	15,468,000	7,750,000	47,371,000	13,164,000	'
Net income attributable to noncontrolling interests	1,348,000	432,000	1,947,000	600,000	'
Tax effect on income recognized	'	'	0	'	'
Distributions to noncontrolling interests	'	'	2,500,000	0	'
Distributions from joint venture	'	'	2,500,000	0	'
Capital contributions	'	'	0	'	'
Cash	1,793,000	'	1,793,000	'	3,565,000
Accounts receivable	8,448,000	'	8,448,000	'	8,843,000
Current liabilities	$8,318,000	'	$8,318,000	'	$9,379,000

Contingent_Earnout_Liabilities1

Contingent Earnout Liabilities (Details) (USD $)	9 Months Ended		1 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Apr. 30, 2013
			Rockford
			2012 earnout target
Contingent earnout liabilities	'	'	'
Cash paid	$2,273	$38,110	$6,900

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2010

SIGI

Roger Newnham

Lemmie Rockford

Quality RE Partners

Pluris, LLC

item

Related party transactions

Lease payments to related party

$379,000

$327,000

$1,176,000

$975,000

$688,000

$695,000

$223,000

$212,000

$68,000

$198,000

Amount of the agreement to construct a wastewater facility for Pluris, LLC

6,100,000

Related party revenues recognized

362,000

Net income

$23,193,000

$17,948,000

$49,126,000

$40,335,000

Number of former shareholders owning leased property

Number of current employees owning leased property

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (2013 Plan, Restricted Stock Units, USD $)	0 Months Ended	3 Months Ended	9 Months Ended
	3-May-13	Sep. 30, 2013	Sep. 30, 2013
	3-May-13	Sep. 30, 2013	item
2013 Plan \| Restricted Stock Units	'	'	'
Stock-based compensation	'	'	'
Shares granted	100,000	'	'
Number of equal installments to vest units over the service period from 2014 through 2017	'	'	4
Number of shares of common stock issued for each unit when vested	'	1	1
Grant date fair value (in dollars per unit)	'	$21.98	$21.98
Compensation expense recognized	'	$138,000	$229,000
Unrecognized compensation expense	'	$1,970,000	$1,970,000
Period to recognize unrecognized compensation expense	'	'	'3 years 7 months 6 days
Accrued dividend equivalent units	'	'	0

Income_Taxes_Details

Income Taxes (Details)	9 Months Ended
Income Taxes (Details)	Sep. 30, 2013
Income Taxes	'
Effective tax rate on income before taxes and noncontrolling interests (as a percent)	38.13%
Effective tax rate for income attributable to Primoris (as a percent)	39.09%
U.S. federal statutory rate (as a percent)	35.00%
Minimum period of statute of limitations of state and foreign jurisdictions	'3 years
Maximum period of statute of limitations of state and foreign jurisdictions	'5 years

Dividends_and_Earnings_Per_Sha2

Dividends and Earnings Per Share (Details) (USD $)	0 Months Ended						3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Oct. 15, 2013	Aug. 02, 2013	Jul. 15, 2013	3-May-13	Apr. 15, 2013	Mar. 05, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Dividends and Earnings Per Share	'	'	'	'	'	'	'	'	'	'
Cash dividend declared (in dollars per share)	'	$0.04	'	$0.04	'	$0.03	'	'	'	'
Total dividend paid	$1,805	'	$1,805	'	$1,547	'	'	'	$3,352	$4,611
Numerator:	'	'	'	'	'	'	'	'	'	'
Net income attributable to Primoris	'	'	'	'	'	'	$21,845	$17,516	$47,179	$39,735
Denominator:	'	'	'	'	'	'	'	'	'	'
Weighted average shares for computation of basic earnings per share	'	'	'	'	'	'	51,568	51,398	51,529	51,387
Dilutive effect of shares issued to independent directors	'	'	'	'	'	'	3	6	10	15
Dilutive effect of shares issued as part of Q3C acquisition	'	'	'	'	'	'	'	'	1	'
Dilutive effect of unvested restricted stock units	'	'	'	'	'	'	100	'	55	'
Weighted average shares for computation of diluted earnings per share	'	'	'	'	'	'	51,671	51,404	51,595	51,402
Earnings per share:	'	'	'	'	'	'	'	'	'	'
Basic earnings per share (in dollars per share)	'	'	'	'	'	'	$0.42	$0.34	$0.92	$0.77
Diluted earnings per share (in dollars per share)	'	'	'	'	'	'	$0.42	$0.34	$0.91	$0.77

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	1 Months Ended			0 Months Ended	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Aug. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Jan. 07, 2013	Sep. 30, 2013	Dec. 31, 2012
	Aug. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Q3 Contracting	Q3 Contracting	Q3 Contracting
Stockholders' equity	'	'	'	'	'	'
Amount received for shares of common stock issued under a purchase arrangement	'	$1,455	$1,240	'	'	'
Shares of common stock issued to managers and executives under a purchase arrangement within the Long-Term Incentive Plan for bonus amounts earned in the prior year	'	131,989	111,790	'	'	'
Discounted price from market price at which shares purchased by participants in LTI Plan (as a percent)	'	75.00%	'	'	'	'
Shares of common stock issued as a part of quarterly compensation of non-employee members of the Board of Directors	9,110	12,480	'	'	'	'
Stock issued to sellers (in shares)	'	'	'	29,273	29,273	'
Price of shares issued (in dollars per share)	'	'	'	'	'	$14.69
Stock issued for acquisition	'	'	'	'	'	$430

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Commitments and Contingencies.	'	'	'	'
Total lease expense	$3,566	$2,629	$11,111	$7,388
Lease payments to related party	$379	$327	$1,176	$975

Commitments_and_Contingencies_1

Commitments and Contingencies (Details 2) (USD $)	Nov. 30, 2011	Feb. 07, 2012	Mar. 31, 2013	Nov. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012
		James Construction Group LLC	Q3C	Q3C	Letters of credit	Letters of credit	Bonding	Bonding
		North Texas Tollway Authority v. James Construction Group, LLC
		item
Commitments and contingencies	'	'	'	'	'	'	'	'
Total commercial letters of credit outstanding	'	'	'	'	$8,123,000	$6,168,000	'	'
Cost to repair retaining wall	'	5,400,000	'	'	'	'	'	'
Number of other walls constructed on the project, which could have potential exposure to failure	'	6	'	'	'	'	'	'
Bid and completion bonds issued and outstanding	'	'	'	'	'	'	1,449,158,000	1,298,589,000
Withdrawal liability recorded	$7,500,000	'	$119,000	$85,000	'	'	'	'

Reportable_Operating_Segments_1

Reportable Operating Segments (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
	Sep. 30, 2013	Sep. 30, 2012	item	Sep. 30, 2012	Dec. 31, 2012
Reportable Operating Segments	'	'	'	'	'
Number of operating segments	'	'	3	'	'
Segment reporting information	'	'	'	'	'
Revenue	$551,333	$431,842	$1,406,341	$1,060,851	'
% of Segment Revenue	100.00%	100.00%	100.00%	100.00%	'
Gross Profit	75,465	56,291	181,098	137,891	'
% of Segment Revenue	13.70%	13.00%	12.90%	13.00%	'
Goodwill	118,626	'	118,626	'	116,941
East	'	'	'	'	'
Segment reporting information	'	'	'	'	'
Revenue	178,716	181,260	544,325	459,167	'
% of Segment Revenue	32.40%	42.00%	38.70%	43.30%	'
Gross Profit	10,600	18,664	40,810	47,442	'
% of Segment Revenue	5.90%	10.30%	7.50%	10.30%	'
Goodwill	70,946	'	70,946	'	69,859
West	'	'	'	'	'
Segment reporting information	'	'	'	'	'
Revenue	362,362	242,033	828,242	567,351	'
% of Segment Revenue	65.70%	56.00%	58.90%	53.50%	'
Gross Profit	62,520	35,602	133,195	84,297	'
% of Segment Revenue	17.30%	14.70%	16.10%	14.90%	'
Goodwill	45,239	'	45,239	'	44,641
Engineering	'	'	'	'	'
Segment reporting information	'	'	'	'	'
Revenue	10,255	8,549	33,774	34,333	'
% of Segment Revenue	1.90%	2.00%	2.40%	3.20%	'
Gross Profit	2,345	2,025	7,093	6,152	'
% of Segment Revenue	22.90%	23.70%	21.00%	17.90%	'
Goodwill	$2,441	'	$2,441	'	$2,441

Reportable_Operating_Segments_2

Reportable Operating Segments (Details 2) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Revenues and total assets by geographic area	'	'	'	'	'
Revenue	$551,333	$431,842	$1,406,341	$1,060,851	'
% of Revenue	100.00%	100.00%	100.00%	100.00%	'
Total Assets	1,019,011	'	1,019,011	'	931,207
United States	'	'	'	'	'
Revenues and total assets by geographic area	'	'	'	'	'
Revenue	'	'	1,393,837	1,053,547	'
% of Revenue	'	'	99.10%	99.30%	'
Total Assets	1,007,980	'	1,007,980	'	920,872
Non-United States	'	'	'	'	'
Revenues and total assets by geographic area	'	'	'	'	'
Revenue	'	'	12,504	7,304	'
% of Revenue	'	'	0.90%	0.70%	'
Total Assets	$11,097	'	$11,097	'	$10,335